If you decide to go with the p5b-deluxe in hopes of sli'ing later, i wouldn't waste my money. It will run at x16 x4, so you will not see a lot of improvement. Instead i would just sell the 8800gts (not now of course but when it starts to get too low end for your tastes) and get a newer graphics card over buying another gts later.
I got my p5b-deluxe cause it is a rock solid board to me. Just make sure you dl the latest bios before overclocking (if you do overclock, but update it anyways).
If you go for the one pci-e route, i would go for the gigabyte ds3.
Go with the g.skill suggested. Also get the zalman 9500 instead (make sure to get some arctic silver 5 with it). I, personally, would get a 7200rpm HDD and use the extra money for a bigger monitor or some good speakers like the logitech x-530's or z-2300 if you have enough money. Just make sure to get a sata 3 gb/s HDD if you do.
Other then that, that system is pretty sweet and will be ready for vista and upcoming games (in dx10 if you get vista later).
CPU: e6600 @ 3.2ghz
RAM: 2GB G.Skill HZ PC6400
Mobo: ASUS P5B Deluxe
GPU: Sapphire HD4870
Soundcard: Creative Labs X-Fi XtremeGamer Fatal1ty
HDDs: 250GB WD + 750GB WD + 2x1TB WD
Monitor: Samsung 226BW
PSU: OCZ GameXStream 600W
Case: Cooler Master Stacker
OS: XP Professional SP3
Mouse/keyboard: Logitech MX518/Saitek Eclipse II
Speakers: Logitech Z-2300