Need help deciding on new receiver

[dgg04]

Hi, I'm new to the whole home theater scene and would welcome some suggestions.

My current set up consists of:

Samsung LN46A550 and PS3

The audio is lacking from the built in speakers, but I've never owned a home audio system before.

After doing some research on these forums I found the following,

Reciever: Onkyo TX-SR606, $319.99
Speakers: 2 x Polk Audio Monitor 50 Two-Way Floorstanding Loudspeaker Cherry Single , 2 x $119.99

I'm trying to keep my budget around $500.00 and plan to fill in the speakers as I get more money with perhaps

4 x Polk Audio Monitor 30 Cherry Two-way bookshelf loudspeaker Pair
CS20 TSi Series Cherry Center Channel Speaker
and a sub woofer at some point

I plan to use this primarily for watching blu-rays and occasionally listening to music. The room this will be in is 13' X 15'. I would appreciate any suggestions you guys could offer on my current choices or a different receiver or speakers.

Thanks!!