They're all pretty good... I have an Asus v7700 pure and its pretty cool. if you want tv in/out and svideo in/out etc, they have a v7700 deluxe. I think leadtek had one with faster memory which would help a lot, but I really dont remember. Check out
tomshardware (in their video guide section). tom's has a lot of good benchmarks.
I'm assuming that by GTS you mean non-ultra and non-pro. Based on
this, the suma 64 meg one seems best (read the link), or possibly
this, which gives the gainward cardexpert gf2 gts the #1 spot. Read both links if you want the whole story.
The reason these 2 cards are "best" is b/c they use faster memory. I know nothing about drivers / features / etc.