new computer

dear 4chan
i am buying a new computer, but not a whole one, i am building it myself, i though it would be easy and it isint, i am a programmer, i dont know shit about hardware, so bare withme, this is what i came up with, so before i buy may i have some suggestions.

1. cpu
--AMD Athlon 64 3200+ 2.0 GHz Socket 939
http//www.canadacomputers/...
$186

2.motherboard
--Asus A8N-SLI Socket 939 NVIDIA nForce4 SLI w/ Dual-Ch DDR400, Gb LAN, SATA 3Gb/s, NV RAID, AI 8-Ch Audio, Dual PCI-E x16
http//www.canadacomputer/...
$144

3. graphic card
--eVGA GeForce 6600 LE / 256MB DDR / PCI Express / SLI / DVI / VGA / TV-Out / Video Card
http//www.tigerdirect.ca/...
$121

4.harddrive
--Maxtor DiamondMax 10 SATA/150 100GB 7200RPM 8MB Cache (OEM)<<
link: http//www.canadacompute/...
$72

5.soundcard
--Creative Sound Blaster Audigy 2 ZS w/ 24-bit Advanced HD, 7.1-channel, 108dB SNR (OEM)
link: http//www.canadacomp/...
$74.99

6. ram
http//www.canadacomputers/...
$55

7. Case
http//www.tigerdirect/...
$58
or
http//www.tigerdirect/...
$80

yea its a nice and cheap one, but i am gonna combine it with the one i currently have, i only have a few questions, first off will the cpu+motherboard+ram be compatiable with eachother, second will my graphic card be compatiable, and third how does SLI work, like maby in the near future can i buy another of the same graphic card and plug em in together?
also if 400W enough to keep everything running stable?

>>15
Just get a 500, if by some magical instance that the power dips and requires more then atleast your power supply can handle it. If you do later on require a larger power load on a future upgrade, atleast you don't have to run out and buy another PSU. They only break down when dirty bastards don't clean out their computer fans.