right now i'm running an old system. the only thing i plan to do is maybe upgrade my video card
cpu- AMD Athlon 3800 2.4 ghz OC to 2.75
Mobo- Asus a8n sli deluxe
gpu- BFG 7600gt - upgrade to 8600GT or 9600GT
ram- ocz value ram
and the psu i currently have came with my case its a crappy raidmax 450w that absolutly sucks and sounds like a vacuum cleaner
That one would power even an HD 4870 X2 and a quad CPU. I have one and can guarantee it's silent. It might not fit in your old case though.
Edit: don't get the 8600GT, it's not a gaming card. I have one on my work PC and it's fine for Office and Visual Studio, but that's about it. The 9600GT is decent. The 9800GTX+ is much better, and the HD 4850 a little better still. The 9800GTX+ is pretty big, so measure how much room you have in the case if you want that one.
+1 for the VX450. My PC is powered by one of these and it's dead silent.
I don't agree with ram1009. Power supplies have the highest efficiency at medium load, so buying a 750W power supply when the system usually uses less than 300 is a waste of money.
well my pc is pretty outdated for any serious gaming thats why i'll be putting together a new build in a few months or so. this will be for general use thats why silence is the priority. the vx450 does look good based on many review but then the silverstone is also every good on the latest 300-500w psu review on anandtech.
Corsair or SeaSonic are probably the quietest. I'd get whichever is cheaper. I'm not sure what other PSUs are worth it from your list. I would also consider the Antec Earthwatts brand PSUs. I have the 500W, and its a good one. I have my computer sitting on my desk, and I can't hear the PSU fan at all. (I can hear the crappy blow hole fan however, it might be masking it.) Newegg sells the 500W Earthwatts PSU for $49.99 with free shipping every now and then, keep an eye out.