I have a dell e1705 still that came with a 7900gs 256mb running at i think 350mhzcore and 5-600 mem,a core 2 duo t5600 2 gig ram and a 80 gig HD. I bios flashed the 7900gs to a 7900 gtx running at 600 core and 800 mem from day 1 and it pretty much doubled my 3dmark 06 score,from 3000 to around 5000.That sure did not help battery life,since i ran the fans on high all the time with some gk.... program.
But it still lives!!! surprisingly with that NV 7900 card overclocked like that for so long.It was lap burner,the bottom got very hot from the memory more then the gpu and cpu i thinks:)
2600k HT on@4705mhz 8gb Cas9 1600 mem 2x EVGA GTX770 4gb Classified cards in SLI @1320 mhz core and 2003 mhz mem,mounted in CM HAF922 with a TX-850 PSU 2xHTPC's 2xi3 2120 3.3ghz dual core,1xasus LP HD6570 1xHIS hd7750@1150core1325mem,55"PanyVT30