Need help upgrading a optiplex 755

[bluelight0-0]

Well I want to get to hard core pc gaming and I got a optiplex 755 the other day.So I said why not make this old thing into a decent gaming pc by upgrading a few things,this is where I need help.i don't know what to upgrade and what to leave alone

Small form factor
Core 2 E6550GHz
4.00 GB of ram
1 terabyte of memory
Windows 7 professional
No sound card
No graphics card

I have around $200-$250 dollars to spend

 

[william p]

Which size case, Mini Tower (MT), Desktop (DT),or Small Form Factor (SFF), maybe even Ultra Small (USFF).
http://en.community.dell.com/owners-club/alienware/f/3746/t/19537919 This will tell you GPUs supported.
GTX750Ti can almost always work. If you want more than that a PSU upgrade is required.
You didn't say which Win7 ,32bit,or 64? If you're interested in overclocking read "Overclocking Dell BTX Computers".
With a 2GB video card you will need 5-6GB RAM DDR2@ 800, with 64 bit OS get 8GB. Get the latest BIOS first. Find out if it's EUFI, or AHCI. Your video card must match this. MT is easiest, PSU and cooling are no problem, DT needs Low Profile video card, and smaller PSU. Core 2 Extreme chips work but BIOS won't recognize them as such. O/C will be limited by 3 phase VRM on motherboard, how much? Nobody knows yet.
So a little more RAM, a GTX750Ti, and either a q9550, or Q9650 will fit your budget.

 

[bluelight0-0]

Ok so I did some research and found that the (sff) can handle a Intel core 2 q6700 2.66 GHz processor. It takes about 95 watts out of 275 watt power supply that the (sff) has.Also found that the (sff) can hold( 4x 2 Gb).the last thing I still don't get and need help with is my gpu. I don't know if I'm going to have to upgrade my power supply if I add a gpu.i don't know what gpu to get or anything like that.

 

[william p]

http://en.community.dell.com/owners-club/alienware/f/3746/t/19537919
There are better CPUs than those Dell listed. When newer CPUs came out they didn't update the list. Kisianik (from here) made them go back and do it.
Q9550,Q9650 are certified by Dell, just not "listed".
Q9650 is 3.0Ghz, with 12MB cache 95W.
There are 3xxx Xeons that are equal to Q9650 but 80W. Lga775 so no adapter. Justajohn say it works with no BIOS mod. in Optiplex 780.

GTX750 Ti comes in low profile and most of them don't require a PSU cable. It's the fastest GPU that runs off of the PCIe slot.