Are there any games in particular you know you want to play or do you just want something that will run CS efficiently?
Consider the size of your monitor and what resolution you are going to have it set to. A lot of the really expensive graphics cards are only needed when your running at a higher resolution. If your going to be playing games at 1920x1080 or less then you can get a lot of very good mid-range cards that will run most games on high/ultra settings.
Read this article (monthly) for the best graphics cards for the money each month. It's sorted into best performance for price and also details the resolution that it performs well or great at.
http://www.tomshardware.co.uk/gaming-graphics-card..
There is also a graphical hierarchy chart on page 7 to show where your current GFX card sits amongst others- and also where your new card will sit. I'd recommend something with 256bit memory interface as a minimum, 320+ would be great if you could afford it. As for memory, 1GB is fine, 2GB optional, and the bits in between you can work out for yourself.
Now that's just the graphics card. You do not need more than 4GB of ram being realistic. Just make sure it's fast ram, rather than having 8GB of slower ram. There's lots of DDR3 1600mhz for silly cheap at the moment, or treat yourself to some of the 1868 or 2000, you can get 4GB of decent 2000 for £90~ ish depending on where you buy it from.
If your going to go with AMD then consider the bulldozer FX chips, they have some nice quad/hex core chips. They are a good bang for buck if you are on a budget.
If your going for Intel, then try and go for the new 3rd gen Ivybridge cores. The K series are the best for overclocking but to be honest they are all going to be very good chips even at stock performance so just buy what you can afford.
Get a decent branded motherboard to house either AM3/1155ivy and also make sure it supports DDR3 and the speed of DDR3 you go for too.
Get 2 hard drives, one SSD for your operating system and one normal SATA hdd for your storage. IF your steam directory is going to be big (IE Lots of games) you might want to install steam on the SATA hdd and not the SSD, as not to fill the SSD up.
You can get 120gb SSD's for £80 now, so it's well worth invested. If you can afford it, then maybe go for a 240GB ssd - circa £140, and get a smaller storage drive (again, all of this depends on your games/steam directory/program files size, and also the amount of films/music/storage you want to have on the computer.
PSU - You probably want a minimum of 520/550 watt, though a 600watt would be ideal. I have a 520 and I run 4hdd's/HD4890+other devices and never had a problem. IF you can get a modular psu then do so, as it will help with cable management in your case.
IF a full new build is not realistic for you, then consider an upgrade for what you already have. If your on a c2duo then your socket type is 775 - and you could get a core2quad off ebay for quite cheap. There are a few types out there but the q6600 or q6850/q9650 are all good chips. Combine the quad core with (maybe) an additional 2GB of DDR2, and a fresh install of windows7 64bit, and you might find your machine runs as good as you want it to. Also - buy a SSD no matter what you choose to do, because it is the single, best upgrade that you can buy if you had to just upgrade one component (even if you just buy an 80 gig, and have all storage on your current 500).
However, a lot of SSD's are SATA3 and I'll guess your motherboard is SATA2 so you wont get the full potential from it (im the same, socket 775 with an intel SSD but the mobo is only SATA2 - but its still really quick).
I hope this helps - feel free to ask any more questions.
Post edited 2012-06-02 11:36:232012-06-02 11:34:44