Graphics card and PSU help

[SlipTwo]

So my computer at the moment has a
E7400 2.80
3gig ddr2 ram
Foxconn G31MX Series MB/ Bus Clock: 266
255w PSU
9400 GT

I want to upgrade the gpu and psu,so i want t know what you guys think.
I have got an Asus GeForce GTX 275 896MB GDDR3 and wanted to know if it will be compatable with my motherboard and what psu would best suit it.Also the card only just fits in my case so would i be better off getting a bigger case.

The other option is what card and psu would you recommend for the pc i have,without changing anything else.Because if i have to buy a new motherboard and case i may just sell the gtx to my friend.I dont know if i want to spend all that money at the moment,plus paying to get it all fitted.

 

[Yami]

The 275 is compatible with your motherboard; any 500W PSU will be plenty for the system. Have a look at the Corsair VX550.

 

[SlipTwo]

My case isnt that big the card only just fits.Should i buy a bigger case for better ventilation and airflow?or is it not that big of a deal