i like most of your choices, but you may want to rethink the video card.  I agree that the X800XL is a great card on paper, but ATI has been pretty bad at supplying its most wanted cards, i.e. X800XT PCIe and X700XT PCIe, so i don't think they are gonna be real easy to find.  Hopefully I'm wrong, but i don't know how much of a chance you will want to take on waiting for one and sitting on a ton of depreciating hardware for possibly months.  And even if it is available, it won't likely hit MSRP for longer still, and at $350-400, it looks a lot less appealing than a $375 6800GT.  Personally, I'd grab a 6600GT (XFX's PCIe dual DVI card is $180, i have one and love it, overclocks nicely to 552/1120MHz) and then look to upgrade around R520/NV50 time, when both companies will have SLI, PS3.0, and possibly even unified pixel and vertex shaders (DX10).  This should coincide with microsoft's avalon release, as well.  I just can't see sitting on that much hardware when ATI's track record recently has been sketchy.
As for other components, I've heard great reviews of the Antec, so i don't think there will be a problem with it.  Just make sure you get a 24-pin ATX2.0 PSU, since PCIe mobos need the more stable power it provides.  My Vantec 520A is great, and is only $90 at newegg.  Just avoid that stupid X-Connect thing like the plague.  Sure it's cool and innovative, but the PSU side of things leaves something to be desired, especially on a PCIe platform.  And if you're going with value ram, get some Corsair Value RAM.  I've yet to find anything much cheaper, and the 2.5-3-3-8 timings are pretty good for $140 for a gig.  Mine are rock stable.  Oh, and how much is the MSI mobo?  Cause the Chaintech VNF4/Ultra is only $120.  I had some problems with it initially, but the newest beta BIOS fixed most of them, and it performs great.  But I have heard good things about the Neo4, so if you find a good deal, go for it.  If it's close to $200, though, get an A8N-SLI instead.
Anyways, those are my $.02