GPU and PSU Compatability?

[TechLovie]

So I have this epic build, I got it for free though. Its a Dual Xeon setup, with 10 gigs of ram. And the rest is normal. Its a Dell precision 690. So I put in a Asus radeon hd 7750 (that needs no external connectors) and I saw that this thing can play games hella good. So I tried putting in a Asus radeon hd 6850 and then afterwards an XFX Radeon hd 7870, but not to any avail. So both these cards need 2 six-pin cables, but the PSU has only one coming out of it. I plugged that one in, and used a dual molex to 6 pin adapter for the other slot. When i boot the PC up, all the fans go max, stay at max, and no screen! Why! The GPU work on the other PC i have though... Any tips? Could I like cut the 6 pin on the PSU and make like a dual 6 pin from that? the PSU is 750 watts so I know that's cool. Buying another PSU is probably not an option, its a PSU that has like 2 motherboard connectors and all.

 

[Dark Lord of Tech]

You need a stronger power supply , with the right connections.

 

[TechLovie]

If you didn't read what i said; "Buying another PSU is probably not an option, its a PSU that has like 2 motherboard connectors and all. "

You need a stronger power supply , with the right connections.