I may end up having to get a new motherboard, and I think I want to get an M-ATX. I want to be able to still have the option of SLI and have space between the cards. This motherboard has a PCIe slot at the bottom of the board, and the Prodigy, Phenom, Colossus M, and the 350D all have 5 slots. Would there be any problems with using SLI with one card in the top slot and one in the bottom slot so they have room to breathe?
the top card will block the bottom card's air flow but there are ways to get around this. It you have 2 cards with the Nvidia stock cooler on the it shouldn't be a big problem, although the bottom card will still be a bit hotter. Which graphics cards do you want to Sli?
Reference cooler 670s.
Ya those are definitely going to not work well. The new Nvidia reference coolers are better for close Sli because they can draw air in threw the fins on the right side of the card. The old reference cooler doesn't have that hole. I'd recommend going with a stock cooler gtx 770 set up with this card: http://pcpartpicker.com/part/evga-video-card-02gp43771kr
I think I'm gonna either stick with ATX or just go full on SFF with M-ITX.
Hey you could go with the asus mars 3 card. It has dual 760's on 1 pcb and 760's are the equivalent of a 670. You may be able to keep the m-atx form factor with that
I don't know how I feel about the Mars 760. I would rather get 780Ti since SLI is usually less reliable than single GPU config, plus I already have a 670.
If you want to do SLI with high-end graphics cards, I would advise you stray away from mATX and build an ATX build. You could fry both of the cards if the case doesn't have enough airflow.