I've got a cheapo lite-on power supply that came with my old 2007 HP Pavillion PC, and I currently run a Sapphire HD 3650 DDR3 pci-e graphics card with no problems at all.
It has 300w and 19a on the 12v rail and I was wondering if I could run an HD 6750. I believe it can as the power consumption on the HD 3650 is around 215 (with a complete build) and so is the hd 6750, but I want to know your opinion.
19A On 12V = 19 x 12 = 228W
Deducting 100W For The Processor(With 10W Headroom Just In Case), We Have 128W Out Of Which The 6750 Will Require A Minimum Of 90W And Max Of 100W, Which Leaves Just 28W For The Rest.
Sadly, Thats Not Good Enough, You Need To Get A 400W PSU With Atleast 25A Or More On The +12V Rail