Well, I'm not a fan of Yamaha's lower-priced receivers right now. Yamaha has skimped on their amp quality the past couple of years and it is actually audible. For a lower-priced receiver, I would really point you towards Onkyo or Pioneer. My personal preference is Onkyo, strictly because I prefer the Audyssey room correction over any other type. So I would swap out the Yamaha RX-V565 for the Onkyo TX-SR607 or even the 507 since it sounds like you're aiming for a 5.1 speaker setup anyway.
If money is tight, the surround speakers are the best place to "skimp". It is far less important for the surround speakers to be a perfect sonic match to the other speakers. Most of the surround channel sound is ambience, so the surround speakers are far less vital.
Do not skimp on your subwoofer! Also, decouple your subwoofer. SVSound's PB12-NSD is absolutely my top choice for a relatively inexpensive subwoofer. If you need lower cost or physically smaller size, the SVSound PB10-NSD is good, as are the HSU VTF2-MK3 or even the HSU STF-2 (although you definitely sacrifice extension and output a bit with the STF-2).
No matter what subwoofer you get, decouple it from the floor with an Auralex SubDude/GRAMMA. I've talked a lot already about the SubDude/GRAMMA, so just poke around some of the other threads here on the front page of this forum and you'll see why
You can also get away with no center speaker if you really need to. You can set your receiver to "phantom" center. The center channel will simply be equally split between the front L/R speakers and you will rely upon their stereo image to create a "phantom" center speaker. with good front speakers that have wide dispersion and good imaging, the illusion of a center speaker can be very convincing and totally diminish the need for an actual center speaker.
So my advice?
Swap out the Yamaha RX-V565 for an Onkyo TX-SR607 or even the TX-SR507.
Get your front L/R speakers. Don't worry about the center or the surrounds for now.
Do NOT throw some spare speaker into the center position. Just set the center channel to "phantom" (the setting might just be "off" or "none") in the receiver and let your new front L/R speakers handle things.
Feel free to throw some spare speakers into the surround positions.
Do NOT skimp on the subwoofer! Get the SVSound PB12-NSD if you can. Get one of the other subs that I mentioned if you can't.
No matter what subwoofer you get, put that sucker on top of an Auralex SubDude/GRAMMA! This is a MUST
Speaker wire and cables do not have to be expensive in order to be good. Check out bluejeanscable.com, monoprice.com and tartancable.com for all of your wire and cable needs!
The PS3 is a GREAT Blu-ray player and a pretty darn good DVD player. No worries at all in using a PS3 as your source!
Best of luck!