How do you have the audio hooked up now from the ps3 to the receiver? If you have an optical cable between the two you should be getting as least DD5.1.
Now as for a new system. There's a lot of talk about the upcoming (I think in April) Yamaha 663, with HDMI1.3 and a nice feature set. It will be on the low side of the budget to give you more money for the speakers if you want. You can also just keep using the ps3 for Blu-Ray, again more money for speakers. Now speakers are where you're going to hear most of the difference. Go out and listen to as many brands as you can and see what you like. There are so many brands out there to look at; Paradigm, PSB, B&W, Klipsch, JBL, Axiom, AV123, SVS.... the list goes on and on.
Go out and listen and let us know what you like.
T