Unfortunately I don't have a suitable power meter to measure my current power draw, but I've only got a slightly OC'd X3 720BE, 8GB DDR2 1066 (although I'm running it at 800Mhz@1.9v at the moment, as I'm having trouble with one of the sticks at 1066Mhz, ultimately I plan to run it at 1066Mhz, which will require me bumping up to 2.2-2.3v) and two HDs.
I've also got an Audiophile 24/96 PCI card, a PCI NIC card, a couple of DVD drives, a front panel USB/SD card bay (which takes power from the PSU) and use a USB-powered 2.5" drive for backups, but most of those won't be in use when gaming, so my Nexus will probably be OK.
You may do some ballpark math: at stock setting your current system should be at high real loads under the 130W DC mark PLUS the drives (we could estimate under 20W for these, at large: they will spin higher, but you don't game at boot). I think that you won't use DVD or USB when gaming, so we may set them apart, there are the sound card and the NIC, I dunno how much it may draw.
Therefore your PSU should be around 11-12dB, a pretty good "value".
Then add 140W for a 6950 at gaming, 300W MINIMUM. OC'ing should add maybe 60W for both CPU and GPU?
A Nvidia card is slightly less friendly, a 30W penalty? Around the 400W mark.
Your Thermaltake thing have the PSU on top, so we may use the hotbox scenario: the best PSUs according to SPCR would be:
oc'ed Nvidia/720 (around 400W)
1) your Nexus Value (430W) ~19dB minimum
2) Enermax 87+ (500W) +1dB
3) Nexus NX5000 (530W) - Seasonic M12D (850W) +5dB
4) Corsair AX850 (850W) +6dB
5) Antec TP-750 (750W) +14dB
stock 6950/720 (around 300W)
1) Enermax 87+ (500W) - Seasonic M12D (850W) ~14dB minimum
2) Seasonic X-650 (650W: and the X-560?) +2dB
3) your Nexus Value (430W) - Corsair AX850 (850W) - Antec TP-750 (750W) +4dB
4) Nexus NX5000 (530W) +8dB
We may say also that the quietest 6950 I'm aware of should be not less than 16dB at load
, while the best GTX 560Ti (the reference design) should be at least 1dB higher. This is therefore about your noise floor.
Both the X-series (Corsair, Seasonic) and Enermax are expensive, the Seasonic M12D should be too and also a bit outdated, the choices should have been worked out, I mean, shouldn't they?
If you want a wider range of options, I think that you should get rid of your Bach VX (nice case, OTOH) for an enclosure with a bottom mounting for the PSU.
Eventually I'd like to stress that it's only ballpark "math"!