WELCOME TO SPCR!!!
CPU: Good! I love my NewCastle; undervolts splendidly while providing very
good performance all the same.
Mainboard: DFI LANParty UT nF3 250Gb is a better choice, "IMHO..." With this board you should be able to undervolt the 2800+ NewCastle to ~1.15V at its stock speed of 1.8GHz without a hitch and the included ITE Smartguardian is an outstandingly easy to use automatic fan speed control and temp. report software package. I also know for a fact that Alex Van Kaam's Motherboard Monitor works with this board just fine.
Combine it with a decent cooler and a case with a side intake duct and you can likely run the CPU without a fan on its cooler (just rely on the CPU and DFI LANParty UT's undervolting features).
GPU: I used to have that exact card. The DX9 is laughable, but if you're fine with slideshow speed, you're good to go. DX8 and earlier are much more acceptable on it, as is OpenGL.
HDD: Is the 8MB version of the 120 or 160GB Samsung that
much more expensive than a 160GB, 2MB model?
Evercase: A fine choice. Also check out Antec SLK3000B.
PSU: Super Silencer 300 is okay;
the fan is not the best in the world, but it's set to spin slower due to the PSU's above average efficiency. This is a great choice for swapping the stock fan and cold air ducting the PSU. If you don't want to work so hard, I'd say go with a Super Tornado 300.
If the price is okay with you, I suggest XP-90, but XP-120 fits the DFI LANParty UT nF3 and it's the one I recommend if you want to run the CPU with no fan on it. Having a case fan and no CPU fan is better for overall cooling than a CPU fan but no case fan.
Suspending the HDD is a great idea, particularly if you go with a Samsung, which makes more vibration than whine.
Enjoy your stay here at SilentPCReview; it's nice to see someone who does reading before
posting, even if they do double-post.