What I would be looking at for $800, if you actually want a good video card, I'd say:
$124.00 Athlon 64 2800+
http://www.newegg.com/app/View...description=19-103-452
$84.49 Biostar K8NHA
http://www.newegg.com/app/View...description=13-138-240
$275.00 256-bit GF6800
http://www.newegg.com/app/View...description=14-145-096
$61.18 Samsung 80GB
http://www.newegg.com/app/View...description=22-152-010
$144.17 2x512MB Corsair
http://www.newegg.com/app/view...description=20-145-440
$42.00 Liteon combo drive
http://www.newegg.com/app/View...description=27-106-932
$76.49 Antec 1650
http://www.newegg.com/app/View...description=11-129-150
That's $807.33 delivered, but it's pretty biased towards gaming. For most people I think you'd be better off spending more on a big hard drive, DVD burner, maybe a nicer CPU or a more exciting motherboard.
Things to consider:
You can save $5 by going with Mushkin memory, which is just fine.
The WD SATA drive you listed costs $7 more but isn't going to make any difference (and many argue Samsung is more reliable).
There's no need for a floppy drive if you slipstream your SATA drivers, and there's no need for SATA drivers if you don't get a SATA drive, and there's no need for an SATA drive unless you're getting a Raptor or one of the nice Maxtors with NCQ.
If you're going to get a GF6800, I would certainly recommend one of the 256-bit ones. If you're not going to get a 256-bit one (i.e. you want to stick to the $200 range), I would recommend a 256-bit Radeon (R9800 XT?). Maybe this has changed in the last few months, but I think the 128-bit 6600 may not be the best deal at $209.
Seriously, I fail to see how a computer upgrade is even relevant to play poker. If that's your main concern, and you really want to upgrade, you might as well get a nice silent fanless $100 - $150 video card and spend your money on other things. The real question is:
1) what are your actual gaming aspirations?
2) how many tables to you play and what site do you play on?
3) do you run poker tracker?