I beg to difference
I have the same exact problem, using an old enermax 435W + GF6800Ultra I've maxed out my 12V rail.
whenever I change the CPU's volt. from 1.65 onward I get serious drops in my +12V (moblie XP).
at around 1.75 which I use for 2.4GHz I have 11.9 Ideal, prompting Nvidia's messages of "had to reduce graphics card performance do to lack of power" and sometimes freezes. obviously I can't play as as soon as I start a 3d app my comp freeze.
of course when I put 1.65V cpu = ~2.2GHz (can't recall right now, something like that) CPU I have ~12.1V and am able to play without nvidia messages.
furthermore all my instabilities, if any, are from 3D and/or video-card related, and have started, if I recall correctly, after adding a dvd burner to my 2 raptors+1 pata HDs+dvdrom+dvd burner+fan farm rig.
so It seems I need a new PSU, only all correct PSUs come with different +12V rails (2-3-4 usually) divided as CPU, PCI-E (sometimes a couple), and all-peripherals (all other) 12V. meaning I will still lack on +12V as peripherals have around 16-17Amps.
so the only solution would be either a single rail +12V PSU or an adaptor from the 6-pin pci-e to molex.
now how to do that?, it is necessary!
P.S.
there's that TK 250W 12V 5.25" PSU:
on newegg (just for example, not connected to them in anyways)
it too has 2Xpci-e 6-pin connectors.
it's relatively cheap and can resolve my problem but for those damn pci-e plugs!
care for a suggestion?