What is really important is the cooling methods (which are usually perfectly fine) and the memory speeds in ns, which is written on the chip. When you're looking at them, try to get the fastest possible memory. Look for lower ns ratings. The speed may also be listed in mhz. Faster mhz is better

I know when they first started coming out, VisionTek (I loved their cards) was equipping them with 2.8ns memory instead of the 3.0ns chips. The difference - at 3.0ns, the memory runs at the rated 325mhz DDR (or 650mhz), while at 2.8ns the card is clocked the same, it should be an easy overclock to 357mhz DDR (or 714mhz) since the memory is
already rated to run at those speeds.