Nothing displayed on boot + £600 upgrade suggestions

[skudzy]

Combining the two points in one here as the upgrade might resolve my initial problem. So I've had my build for about 3 years now with no issues until it froze up the other day. Hasn't started up properly since. I press the power button and everything looks and sounds like it's on but absolutely nothing is displayed on the monitors. They look like they don't even get a signal (eg a 'lit' blank display). I've tried a barebones boot with just motherboard and graphics card but still nothing. Also tried resetting cmos. Any thoughts on this? I'm thinking either power supply or graphics card is the problem.

This whole thing has prompted me to start thinking about doing an upgrade as it's been playing on my mind. Below is my current spec (excluding HDD) and I'm looking to spend up to £600. I occasionally play games so want a decent graphics card (1024Mb GDDR5?) but general speed of running things is important to me. What suggestions do you have on improving my spec? What are the weak points?

Very much appreciate any and all help and comments on this.

Current Spec:
Abit IP35-E (Socket 775) PCI-Express DDR2 Motherboard
Antec P182 Super Midi Tower Case - No PSU (Gun Metal Black)
Samsung SH-S203BEBN 20x20 DVD±RW Dual Layer Serial ATA ReWriter (Black)
OCZ 2GB (4 x 1GB) PC2-6400C4 Dual Channel Platinum Revision 2 XTC Series DDR2 (OCZ2P800R22GK)
Intel Core 2 Quad Pro Q6600 "Energy Efficient 95W Edition" 2.40GHz (1066FSB)
Corsair HX 520W ATX2.2 Modular SLI Compliant PSU (CMPSU-520HXUK)
OcUK GeForce 8800 GTS 640MB GDDR3 HDTV/Dual DVI (PCI-Express)

 

[skudzy]

Apologies, but just in case this got missed and someone might be able to help me out I'm bumping this the once. Been without a working pc for a week now so hoping for some advice.

Cheers.

 

[skudzy]

Thanks for the suggestions. The motherboard has never emitted beeps on start up and there is no indication of LEDs that mean anything. I've tried booting with one stick of RAM and switching it around but still nothing. Unfortunately I don't have spare parts to swap in and out so I might just go ahead and order the upgrade parts. If it doesn't work after fitting the new stuff then it's obviously the power supply and I'll have to replace that as well.

 

[skudzy]

I quite like the look of olivier renault's first set. If I need to replace the power supply then I was thinking of the Corsair TX 650W ATX SLi Compliant one (or should I be going for less than 650W?).