Hello, this is my first time asking a question on dell.com so if this is in the wrong place please let me know, anyways

I have a Dell Optiplex 745 SFF with 275w power supply, one 80GB harddrive (I will upgrade to 1TB), with 7GB ram (3X2GB DDR2, 1X1GB DDR2) Core 2 Duo E6400 2.13Ghz, R5 240 1GB low profile Graphics Card (50w), and I unplugged the cd drive so that it will waste less watts. I wanted to upgrade the Processor to a Core 2 Quad Q6700 2.66Ghz but ever since I added the graphics card I was worried that there wouldnt be enough watts to handle the Q6700, I did read some posts that said when you go over your watt limit it may cause the power supply to burn and stop working, can anyone tell me if it will be ok to replace my Core 2 Duo E6400 with Core 2 Quad Q6700 2.66, and please keep in mind that I have an R5 240 in the pc. If it wont work then should I get a Core 2 Duo E6700 instead.

Thank You for ANY help