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Hi there,
Welcome to the community! 
Having checked your TV user manual I notice that your TV supports a feature called 'HDMI-ARC', ARC stands for 'Audio Return Channel'. Basically this would simplify connection of your TV to your new Receiver and allow both devices to be controlled from one remote. I believe you would also get sound coming out of both devices unless of course you choose not to. An option on your TV can turn the TV speakers ON or OFF. I'm not feeling well today so please forgive me if I'm giving wrong information here, I would recommend reading the HDMI link at the end of this post for a better understanding.
Your TV manual gives this advice in this situation - you would connect your TV to your new receiver as follows:
If connecting a digital audio system that is compatible with Audio Return
Channel (ARC) technology, use HDMI IN 2
To answer your second question; "does the actual Receiver have built in speakers for audio too?"
NO, you would either need to use your existing speakers or buy some new ones. The STR-DH550 supports upto 5.2 channels audio meaning you can have 5 speakers plus 2 subwoofers.
As for using your soundbar, unfortunatly my knowledge is lacking in this area but if it is a powered soundbar you might not be able to use that. Hopefully another user can confirm or deny this last paragraph.
You can read more about HDMI-ARC here: HDMI ARC is the coolest TV feature you’re not using (here’s how)
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@Anonymous
Thanks for clarifying the question about the use of a soundbar. Regarding the audio from the TV, I guess I should have read the TV manual myself more thoroughly but as I mentioned earlier I'm feeling rough today. 
It's my excuse and I'm sticking to it.., LOL!!
You mis-spelt 'rough' - its ruff 
Im barking mad !
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Nope! You're wrong also, maybe you're referring to the slang word perhaps?
The definition of ruff is as follows...
- 1.a projecting starched frill worn round the neck, characteristic of Elizabethan and Jacobean costume."an Elizabethan ruff"
- 2.a projecting or conspicuously coloured ring of feathers or hair round the neck of a bird or mammal."a ruff of long pointed feathers"
I haven't shaved for a week, therefore I'm rough!! Fancy a stroke?
Barking mad? Most certainly......:smileylaugh:
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Yes I can only echo what @Anonymous says here, the receiver you're planning to buy is a fine piece of equipment but adding cheap speakers would be pointless. As Quinnicus says, they'll work but the sound quality will surely be lacking. It's a little like buying a Rolls Royce and putting bike tyres on it, it might still get you from A to B but the ride would be very unpleasant.
20 years ago when I first got into Home Cinema I spent a lot on a Sony Amplifier which of course was my first mistake as I should have bought an AV/Receiver instead. Lesson learnt!!
After a very short spell with that device and feeling very disappointed I ditched that in favour of a Technics AV/Receiver and voila, my listening enjoyment was suddenly changed over night. However, I soon realised that the £60 Sony speakers just weren't up to the standards required for home cinema and lacked the bass to handle anything more than a feint crack of thunder. Again these were quickly replaced with yet another set of speakers from Tandy (do they still exist I wonder)?? Sadly my lesson was a hard one to learn as these too failed to deliver.
Eventually I realised that the only sure way to buy the right speakers was to start reading the What HiFi & What Home Cinema Magazine and see what they recommended. Sure enough within a very short space of time I had become a self styled audio enthusiast and armed with a new credit card I hit as many listening rooms in Tottenham Court Road in London as I could find. In case you've never been, Tottenham Court Road is one of the best places to barter for cash, or at least it was back then.
Eventually after a few trips I selected the speakers that I am still using today, 'Bowers & Wilkins - Rock Solids'. With 150 Watts output each they sure do deliver considering their small size. I have never once regretted buying these speakers and they all sound as good now as when I first bought them 20 years ago. How much did I pay for a pair? Well after a little bartering I got them knocked down from £199 to £150 which was quite expensive back then. Coupled with my Yamaha Active Subwoofer and Jamo Centre Speaker I couldn't be more happy. I'm not sure my neighbours would agree, they don't stick around long!! 
Moving on, last April I had to buy a new receiver as my much cherished Technics unit started smoking! (I think it was stress)!! After doing my research I bought a Sony STR-DN1040. Of course now I had a new dilema, I wanted more speakers and so in the vein hope of finding some more B&W Rock Solids I hit the pages of eBay. Amazingly I found a number of people selling these very same speakers and within the space of around 3 weeks was now the proud new owner of 4 more!! Total cost £150, not bad considering I paid that for one pair originally. I now have a 7.1 setup and all speakers are matched, which is something I would recommend you also consider. Tonal quality is everything and you can't beat matching speakers for that. You can buy some great speaker packages these days (see link below).
And so the moral of my story is.., do your homework! Read some reviews and where possible always try to audition any speakers you're planning to buy in a listening room. If a shop doesn't have a listening room move on and find one that does. Never ever buy speakers without first listening to them and preferably with a variety of different media. Many HiFi shops are geared up to helping customers in this respect and often you can audition the receiver at the same time, heck Richer Sounds even made me coffee!
To help you along your way you might find this link helpful, the reviews should help guide you into making an informed decision and hopefully avoid the mistakes I made along the way.
Speaker packages reviews & products
Wishing you well in your quest and hoping to chat to you some more when you're up-and-running with your new rig.
All the best! 
EDIT:
As one final piece of advice, it is important when buying speakers that the impedance or 'ohms' rating is equal on all speakers. The STR-DH550 is rated as 6-16 ohms, therefore you should buy something within this range. For example '8 ohm speakers' would be fine.
If you havent found it yet you can also read the manual for this receiver online here:
MULTI CHANNEL AV RECEIVER (STR-DH750) / (STR-DH550)
I couldn't mention Bowers & Wilkins without providing a link: http://www.bowers-wilkins.co.uk/
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