Prime 95 really push your system. Which program did you use to overclock your gpu? I suggest MSI Afterburner. It was able to detect my GT 240 while others couldn't. As for the two graphic cards, I would get the 6770 but wait for a good MIR offer. http://www.hwcompare.com/5682/radeon-hd-6750-vs-radeon-... The 6770 will use more power [obvious] but you will get better performance and the 6770 should last you. My friend plays high setting with his 5770 [6770 is rebadged 5770] on games like WoW, Starcraft II, and League of Legends with amazing fps. I know they're not intensive games but the 6770 will be able to handle more.
If it helps, he uses a Hannspree 28" 1080p or something like that.
I would go for nVIDIA due to stronger driver support. I would say between the gt 240 and 4670 is pretty even though. You have a 5670 [I'm not up to date with graphic cards haha]. 450W minimum recommended for 6770. I wouldn't get the 6770 unless you're using a reputable power supply that can handle overload [Antec, Corsair, Seasonic, XFX/ Anything made by Seasonic]
^ nvidia doesn't have "stronger driver support", they have issues like everyone else on occasion. My AMD card works flawlessly as did my previous Nvidia card. It has literally been at least 8 years since i can recall actually having a driver issue with either brand.
I Am using the 6750 right now, couldnt buy the 6770 as it was out of stock. and at 1280 x 1024 , it maxes out all games on high settings. even crysis 1 nd 2 runs well at ultra, 4AA without Dx11. haven't tried the Dx11 patch yet because of slow internet connectivity to download it.
Basically the 6770 is more powerful than a 6750, but at resolutions lower than 1600x900 you won't see much of a difference. Also, my 6750 is overclockable upto 840 Mhz nd 1200 Memory(tested And verified by Furmark).
I Use It At Stock (720 Mhz) i haven't had to overclock it for any game till now.
Also the max power usage of a normal 6750 is upto 90W, and 6770 is 110W, a difference of just 20W. but while overclocking, the difference might increase.
my final verdict is, if you have the money for a 6770, then get it. A 400W 80+ PSU With Atleast 25A on Its 12V Rail Will Handle the card well.
Just post your ratings of the psu, its make and model here and we will tell you.
also post which CPU you are using, amount of ram,Hdd's etc.
Furmark is a software used to test GPU stability nd temperature. However it stresses the GPU a lot more than any game would, so adjusting your OC according to furmark will always ensure you are safe!
yeah, which PSU, open the case and look at its side. there will be the manafacturers name and logo on it.
also there will be a table with all the ratings in a table. like, there wll be values against 3.3V,12V,+5.5V Etc.
Post The Votage reading and ampere reading against each voltage here