SLI and Crossfire Issues

[r3claimer]

I'm thinking of building my own computer. (Which I have never done before.) I had most of my components all selected, and then came the video card. I had heard that the best idea for budget systems, (I'm looking for a build around $1200 [$100 up or down]) is to use 2 moderately good video cards instead of 1 amazing card. I decided on 2 Nvidia GeForce 8600 GTS cards, as they would only total $200. But I recently learned that you need a special motherboard to run multiple Nvidia cards. I would really like to know everything you can tell me about SLI. Also, does ATI's crossfire supported cards require special motherboards?
My biggest questions: Is an SLI motherboard upgradable? If so, only to Nvidia cards? If not, to I have to buy A completely new motherboard?

Maybe it would help to list the components I have selected for my computer.

Intel Core 2 Quad processor Q6600

Intel Motherboard D975XBX2 (I think I can upgrade it to Core 2 quad extreme later)

Nvidia GeForce 8600 GTS 256mb DDR3 (Hopefully 2)

700w power supply

Sunbeam Transformer Case - Black/Green

CD/DVD dual layer combo drive

3gb of DDR2 RAM

320GB Hard Drive 7200RPM

Windows Vista Home Premium

If ATI Radeon doesn't require a specific motherboard, which 2 could I use with my system? (Closest to the 8600GTS.)

And again, I need all the information I can get on both Crossfire and SLI. Thanks in advance.

 

[Matthew DeCarlo]

The motherboard has to specifically support the technology you wish to use (be it SLI or CrossFire). That said, you are much better off getting a single 8800GT or 9600GT for $170-$200.

Clarify what you mean by this:

My biggest questions: Is an SLI motherboard upgradable? If so, only to Nvidia cards? If not, to I have to buy A completely new motherboard?

Also, you do not need a PSU rated for 700w.

 

[nickc]

It does not matter which way u go on SLI or Crossfire, either one will have to have a special board for which one u are going to do. I myself would rather have any Nvidia card because of drivers but that is just me, also are u a gamer if u are get one good card now and the second when u can afford.