Power Supply for HD 6850 (maybe Crossfire)

[absxiith]

Hello,
My GPU is a Sapphire HD 6850 and my PSU is a CoolerMaster eXtreme Power Plus 460w.The CM has worked flawlessly for almost a year,but now the voltage reading in GPU-Z is showing occasional dips to 12.06V at idle from 12.13V and under load,it dips to as low as 11.88V.I wanted to know whether this is normal for a PSU or not?

http://gpuz.techpowerup.com/12/04/19/4bd.png

If not and if it's time for an upgrade,I have decided on either of these-

http://www.ebay.in/itm/CORSAIR-GAMING-GS600-POWER-SUPPLY-SMPS-GS600-VATPAID-BILL-WARRANTY-/190667622138?pt=LH_DefaultDomain_203&hash=item2c64ad06fa

http://www.ebay.in/itm/CORSAIR-TX650V2-650W-80-Cert-Power-Supply-TX650-V2-/280718984677?pt=LH_DefaultDomain_203&hash=item415c27c5e5

I may Crossfire it with another 6850/6870 whenever I have the cash for a decent Motherboard(Presently,it is an MSI MS 7525 ) but if I upgrade to a new PC altogether(not for a year at least),I will buy a new GPU.I just wanted to know,which one of these is better?Will it support Crossfire and will it last me for some time to come?Also,my games(Need For Speed Shift,Mafia II etc.)stutter a lot,even though they are properly patched and original.Is it because of my present PSU?
Edit:My games work properly now after updating my sound card drivers.

 

[simon12]

The TX series PSU has 4A more on the 12V rail so is slightly better both I think has the same efficiency rating.

 

[inzone]

I would definetly go with the 650w psu or maybe a little higher if your trying to plan for the future and at this moment you really don't know what you are going to end up with. If your planning on the right now situation with one 6850 and getting another then a 650w psu will be fine for that . If you have intentions of getting other cards later to replace what you have now and want to keep what ever psu you get now then you have to plan on a little bigger psu because you don't know what you will be getting for video cards.

 

[absxiith]

simon12,Is it because they both have 80 plus bronze rating?
inzone,You are right,I am confused about what I am gonna do . And I am stretching my budget for the TX650,so I just wanted to know whether it justifies the extra 27$ or so.I won't be buying a very powerful single GPU,maybe something mid-range in the future.
So,if I crossfire,does the GS 600 support it (the HD 6850 uses one PCI-E connector and it has two)or the TX 650 is mandatory?
Oh,and is the GPU-Z graph okay?Or is something wrong?It's better if I can postpone it for some time to come,but if it is absolutely necessary,then I am ready to buy.
And simon12 and inzone,thanks for replying.