Switching receivers but not speakers

[abizzle]

I'm a n00b when it comes to this so, I ask that you take it easy on me my first go around with this. Here is what I want to do, and need some input. I currently have the Yamaha HTR-5920 surround sound system, and I am hooking up a PS3 (for blu-ray movies only), a Toshiba HD-DVD player(i know it's obsolete), X-Box 360, Sony 5 disc DVD player, and a TiVo. Now I have been slowly upgrading my home theatre system and I was looking at replacing the whole sound system, but after much thought, I was thinking of just replacing the receiver with the Yamaha RX-V663, keeping the current speakers I have (which came with the HTR-5920) and adding the 2 surround sound speakers in to give me the 7.1 surround sound system. What is your input into this, what should I do? Please help me. If you need any more info, let me know and I can provide it, if I know what it is.