Now i have :
Intel Core 2 Duo E6750 @ 2.66GHz
Gigabyte P31-S3G mainboard
RAM 4GB 800Mhz DDR2
Nvidia GeForce 8800GT 512Mb -> have already ordered a Gigabyte GeForce GTX 560 Ti OC, 1GB GDDR5
So im looking for the options for replacing my processor without changing motherboard, so what would be the best choice for me?
I've been looking for some Quad core processors but i can't decide what would be the best for me
What is your budget? The best processor that is supported by that motherboard is the Core™ 2 Extreme QX9650 but at $900+ for new, I don't really consider that reasonable. Actually, what I did find in the Q/QX series that were "reasonable" were used for $150-$250 on Ebay - I prefer to purchase processors new.
Here's what I did to find that. At the Gigabyte website for your motherboard, they have a processor support list. All of the processors on that list that do not have an N/A in the "since BIOS" column will work with your motherboard. Copy the processor you're interested in, paste it in your favorite search engine, see what you come up with.
Did the same thing you did about a year back, trust me getting a new mobo will be money well spent, dont bother getting a new cpu for a LGA 775 board.
Since its a P31 chipset the best cpu would be an E8600 (depending on bios, etc) since quad cores aren't supported on P31 mobo's (trust me i learned the hard way....)