OC video card = sure thing, why not.
OC CPU = possible even with cheap Epox/Chaintech boards. Instead of spending extra on motherboard (some premium boards cost $200+) just spend the extra amound on a faster CPU from the start if you want to spend that extra amount.
Value RAM = should be called "best value" RAM. There is 100%
no need for expensive RAM even if you are overclocking. Only reason for expensive RAM is to win benchmark bragging rights. You'd be MUCH MUCH MUCH better off spending that extra amount on a faster video card or CPU to begin with.
CASE = Out of those Cooler Masters you linked to, I personally like the Centurion 5. Not counting just those cases... there's a bunch of nice ones out there. I like the Lian Li PC-7 Plus, Antec Super LAN Boy, Antec SLK3000B, CompuCase LX-6A19...
Sounds like you are a gamer (due to your video card choice) so prioritize that aspect... video card is top as long as you have
any socket 939 CPU and
any 1GB RAM. Monitor is probably second choice because after all what good is even a $3000 system if you are left only with enough money to buy an old, used 15" CRT. Lemme use some analogies...
What good is buying a $60,000 Corvette for autocross racing if you spent so much money on it that you can only afford econobox tires?
What good is buying that awesome $2,000,000 home in the best neighborhood if you can't afford furniture after the monthly mortgage payments?
What good is buying an expensive $5000 stereo system if you are only left with enough money to buy those $90 speakers someone was selling out of the back of a van parked at your local mall?
BTW, if anyone trys to sell you speakers out of the back of a van with whatever claims of a great deal, know that you are
getting what you paid for, $90 speakers.
You are already doing well by choosing the video card that you listed, 90% of top performance for 70% of the price. Next is to choose a monitor. Best deals are probably 19" LCD. You can go with a 19" widescreen (Viewsonic at Costco $299) if you watch a lot of movies on your computer. You can allocate money like this:
video card $300
monitor $300
hard drive $130
motherboard $80
case $80
power supply $80
optical $45
keyboard/mouse $60
2GB value RAM $170
CPU $225
= $1470
Hopefully you've got tax/shipping covered, or just knock some back on the CPU or RAM.