help with graphics cards, psu's and motherboards..

Hi everyone!
I have the following system:

LC POWER 550W SILENT GREEN POWER PCIe
ASUS P5B CHIPSET 965 SOCKET 775
CORE 2 DUO E6400 2.1GHZ
4 gb memory ddr2-800
Radeon HD 4850 512MB

And i wanted to upgrade the graphics card to either the HD 6850 1gb or the gtx 460 1gb..
The problem is that all the 6000s are all PCI-E 2.1 and they are known to have issues with PCI-E 1.x. Its not always the case, but there are some reports.. i did some research and apearently its a hit and miss and is dependent on the motherboard... while 2.0 works perfectly.. so if go with the 6850 and risk it not working on the motherboard.. unless anybody ever tried a 2.1 graphics card on a P5B (P965)? Or any similar card? and could tell me if it works?

The problem with the gtx 460 is im not sure if the psu can handle it... any input in that would be apreciated..

A quick note, is that i have no intention of overclocking any of these components.

Try getting a used GTX460 for about $100. Your PSU should be fine if it can meet it's rated specs.

Someone told me this "However, with only 24A on the 12V, I have some doubts about the PSU running a GTX460 though. " so i stayed unsure about the gtx 460.
Here is more details on my psu:
http://www.lc-power.de/index.php?id=46&L=1