2x Video Card Questions

[Aenar]

I've come to the conclusion that I need to upgrade my Video. I'm currently using two video cards, both 512MB XFX nVidia GeForce 8600GT. I don't use SLi and don't plan to as I upgrade. I run three monitors (2 slaves | main | 2 slaves).

I've been eyeballing this card recently as a possible upgrade:
http://www.newegg.com/Product/Produc...82E16814150439

But there is no simple solution to running three monitors off one card. I've looked at external devices as well as cards with 4 DVI ports. I can't justify that cost to myself. So, my questions are as follows:

Can I run that 1GB card with one of my 512MB? I assume yes, as both are nVidia (And both made by XFX to boot).

Will Windows 7 utilize the 1GB card to full potential or will the card dumb-down to the 512MB level? I believe it should only dumb-down under SLi conditions.

Does it matter how I plug in my monitors, like my main monitor onto the 1GB for max settings with slaves only on the 2nd card (both cards have two DVI ports)? If it doesn't matter then does the OS & hardware determine which monitor has the most demand (50/25/25%) - or does it divide resources equally (33/33/33%), even though the slaves are capped @ 20fps & have low visual settings?

In Windows7 do I need to indicate to the system which card I want as primary? Or is that based off the order put into the motherboard (I remember ram slots had numbers like 1,2,3,4 or 0,1,2,3 - thinking PCIe slots might have something like that on the mobo).

Is the newegg choice sufficient or do I need to go bigger for smooth gameplay? It seemed after the $200 mark that its just diminishing returns as the price increases.

For reference, my pc specs
Power - OCZ 700w
RAM - 8gb of DDR3 1600MHz
Motherboard - Asus Evo...something or another
Processor - AMD Phenom II 3.2GHz Quad-Core
Hard Drive - 500gb Western Digital 7200RPM with 32mb cache
3x LCD Monitors (1x 22" wide-screen, 2x standard 19") 2x-1X-2x screen setup