[Freakin]

1. I second the nForce motherboard instead of the Via board.
2. Get 2x1024 of your memory instead of 4x512. You'll be able to upgrade later if you want
3. What's your reasoning behind gettting 3 harddrives in your system? Are you planning on mirroring the two 10k drives? I would personally get a 74gb 10k Raptor and get something like a 250gb, 7200rpm, 16mb cache hd for misc data. Use the raptop as your boot drive and programs and stuff
4. Get a DVD burner (at least a DVD rom). It is increasingly common for games to come on DVD, and you're gonna be kicking yourself if you don't have a drive for them. Also a DVD burner is an EXCELLENT way to backup cheaply. Right now it's like $.20 for 4.7GB... You might as well get a dual-layer burner (for like $50) so that you can burn on the dual-layer discs when they become readily accessible.
5. I don't see a case on there. Make sure you get a good powersupply. The 7800 is a power hog, and if you have 3 harddrives you're going to need some juice.

You've got great ideas for overall specs, but it needs some fine-tuning. And that mouse looks pretty cheesy... but that part is personal preference.