New Build + Swapping some parts

Approximate Purchase Date: By the end of the August of September

System Usage from Most to Least Important: 95% Gaming, 5% General Usage

Parts Not Required: Keyboard, speakers, monitor, OS

Preferred Website(s) for Parts: newegg.com only

Country of Origin: United States

Parts Preferences: AMD / ATI

Overclocking: Possibly

SLI or Crossfire: No

Monitor Resolution: Depends on the game.

Additional Comments: Will be using current sytem's PSU.

Hello all!

Im going to be building a new system in the coming month and i was looking to see what you guys think. My situation is a little different than most because what i am trying to do is keep my current system for gaming for my wife and then build a new system for myself for newer games. The thing is, i will be keeping my current systems case and PSU so i will need to replace the psu and the case in this system. The case i already have picked out so basically let me break this down.

I basically need to know 3 things. 1) Whats the lowest watt high quality psu that i can get to still run this comp for my wife? 2) will my current psu work for my new build? 3) What do you tihnk of the new build parts?

My current system is: MSI k9a2 platonum, phenom II 920, radeon 4850, kingston hyperx ddr2, corsair 750 http://www.newegg.com/Product/Product.aspx?Item=N82E168...

New System:

MOBO: ASUS Sabertooth 990FX AM3+ http://www.newegg.com/Product/Product.aspx?Item=N82E168...
I would really like to stick with AM3+ that way, the cpu i get i can replace the cpu in my current system (soon to be wifes) with whatever cpu i get for my new build if i decide to move to a bulldozer.

CPU: Undecided. This would eventually be migrating into my current setup but i have 3 im currently looking at
1)AMD Phenom II X4 955 Black Edition http://www.newegg.com/Product/Product.aspx?Item=N82E168...
I chose this because i could always get this temporarily to save some money on the build but then if i migrate it to my current setup it will still be a significant increase.
2)AMD Phenom II X4 980 BE or 975 BE This would give me better performance but cost more. Just a choice.
3)AMD Phenom II X6 1100T Black Edition http://www.newegg.com/Product/Product.aspx?Item=N82E168... I know all the reviews and such say theres no benefit and a x6 might be lacking because of the cores not used but i have this as a choice because in the future if games start using more cores and i migrate the cpu to this system it will allow it to go a little further. Make sense?

Video Card: SAPPHIRE 100314-3L Radeon HD 6870 http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Hardrive: SAMSUNG Spinpoint F3 http://www.newegg.com/Product/Product.aspx?Item=N82E168...

PSU: Now the psu i already use in my current system. The psu is a corsair 750 http://www.newegg.com/Product/Product.aspx?Item=N82E168... and i am wanting to use it in the new build and replace it in my current build with CORSAIR Builder Series CX500 http://www.newegg.com/Product/Product.aspx?Item=N82E168..., would that be overkill for my current system or to little?

Memory: Kingston HyperX 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) http://www.newegg.com/Product/Product.aspx?Item=N82E168... Love kingston

That looks like about it. The case i have already picked out, all the little odds and ends i have picked out. Just lookin for the core stuff. I know this is kinda confusing (or maybe IM just confusing) but just let me know if anything needs clarification!

Thanks guys!