Since I'm building a gaming system around X58, I'm essentially doing the same research as you. You have a solid list overall...all I can add are comments and a suggestion here and there.
I'd get at least an Antec P182, or a Cooler Master Cosmos 1000. A big steel case will absorb sound.
[90%] Corsair 620HX
(...or would a 750TX be just as good & quiet, but with more power? they pretty much cost the same around here.)
Unless you plan on serious overclocking or multiple high-end graphics cards, a smaller PSU will serve you better by being more efficient and quiet. A VX450 should be more than enough. Here's a more intense system than yours that maxes out at around 370W
[90%] Noctua NH-U12P SE1366
(...or the ProlimaTech Megahalems?)
Noctua's a solid brand. I'd personally would get a Mugen II to save money and b/c it's more efficient than the Noctua. This chart
from Xbitlabs should help.
[90%] Gigabyte GA-EX58-UD4
(...or the UD4P?)
It's hard to go wrong in this range. Personally, I'm getting an Asrock X58 Extreme, and I've heard good things about the ECS Black X58B-A, both of which could save you a little bit of money.
Western Digital, in my experience, has been more reliable and quiet than Seagate. Personally, I was fine with your first choice, the Green.
[50%] Crucial 6GB kit (2GBx6)
(or the Corsair TR3X6G1600C8D 3x2GB? they cost twice as much though.)
They're absolutely solid. This comparison test
should help you feel confident with the Crucial. I personally am getting $86 PQI memory
since I have no interest in overclocking RAM and just want quantity. Plus it looks pretty cool.
[0%] GPU ...no idea whatsoever about what graphics card i need to get hah... something that stays quiet, works and doesn't get in the way (for about 50$) would be great... could someone please recommend me something like that?
There're fanless GPU's out there...I'd get dual DVI outputs in case you ever want 30" monitors (and there's less of a chance, as minuscule as it is for interference). This one
only takes a single slot and is $63. If you're willing to fill out a rebate and have a GPU taking up two spaces, there's this $57/42 card
Btw, I hope you're getting two LCDs right, with more than a TN panel?