Version doesn't really matter, depending on what you want, but your Motherboard will dictate that, by version. You can use just about any PCIe video card.  www.geeks.com has them DIRT CHEAP, where I got mine for 20.00 with 256MB DDR2 memory.  It frees up shared memory, and is faster than the on-board video, unless you have DDR2 controller, and are using DDR2 memory on the motherboard.   They are all PCIe 16x right now.  The VERSION doesn't have anything to do with that SPEED, is has to do with the per lane memory date rate:

v1.x: 250 MB/s
v2.0: 500 MB/s
v3.0: 1 GB/s

Your manual for the PC or Motherboard will tell you the version.

So, if you are 1.0, you can use a 2.0 card, you're just restricted to that data-rate.  You can even get a 128MB PCIe card for 15.00 at www.geeks.com - so, go there and get a decent card.  Yes, they have 512MB and 1024MB with HDMI ports too.  It is a cheaper route than buying more DDR memory for your motherboard, unless you're at DDR2, which is cheaper, MUCH cheaper than DDR PC3200.