the Q35 is a cpie 16 1.1 interface that supports ddr2 8 gb 800 5.5.5 mhz1333 and any socket 775 processor all the way up to the 3.0 Quad 1333 fsb.
Depending on your ram, processor spec i dont know. Supposed you have the above, about any R9 series ati would be nice and any Nvidia GTX or TI would work. I have a HD7970 with my q35 and the above. if you had say a E8400 processor 3.0 or 2.6 1333mhz i would go with a 6xxx series ati or 6xxx series gtx if you got at least 4 gb of 800 memory. If you got a base unit of 2gb ram any speed, and 2.2 Duo I would go after a 128 Bit 1-2 gb ddr3 (or 5) Graphics card non powered. As it gets its power from the slot. So there is high to mid to low end Q35 system requirements. Looking at 40 bucks for low end, 80-120 bucks for mid and 150-300 bucks and no more for high end on this chip set.