Would it be better to get one high end graphics card, lets say a GTX 295 or a 4870 X2. Or would it be better to get 3 mid range cards, like 9800 GTX, GTX 260, 250, or 4850, 4870 and run them in tri sli?
-3val
It's not really about the heat/load. It's more about the SLi architecture. It never scaled perfectly with 2+ cards. What this means is adding another card doesn't give 100% more performance. For example, adding a second card to a one card setup may only give you a 70% increase rather than a 100% increase that makes sense. Adding another card to that setup may only increase performance 30% and so on.
Yep, go with the single card. GTX 295, or a 4870x2. Go with the better deal, or the one that comes with a better game/deal. I'm no fanboy, so saying which one is better is negligible. Physics/Cuda on the Nvidia graphic cards are doing way better than the equivalent of ATI graphic cards, so that could way in your decision.
If you have time to wait, you could wait for the DX11 cards coming from ATI later this year/early next year. Expected to be way faster than the current DX10 cards while being at the same price point as the 4850/4870/4870x2 when they came out.