RCH37401 wrote:After making sure that works, what will I have to change next? Will I need to change the motherboard or just the RAM and CPU (and processor at a later date)?
Depends on what CPU you want to upgrade to. For example, if you set your heart on an i7-2600 (socket 1155) it won't fit your motherboard (most probably socket 775) and newer DDR3 RAM modules are unlikely to fit either.
I feel that deciding on what CPU and motherboard you want to end up with should be your starting point, I'd advocate swapping those first but as you seem to be in dire need of a new graphics card first that's not exactly practical.
As with any upgrade cost is a big factor, the 'standard' 560 (336 cores) comes in around £140 with the Ti (384 cores) being £40 or so dearer. Add another £40 to get into Ti (448 cores) territory.
Performance wise, the Ti seems to come in about 10-15% more powerful than the standard 560 in benchmarks, but whether this level of improvement would be attainable, or even noticed in RW is unknown.
Size DOES matter, it'd be silly to buy a card you can't physically fit in your machine but as you have a 9800 already I expect a 560 series will fit but it'd be prudent to check specs and get measuring before placing an order. Make sure your PSU is up to the job, nVidia recommend at least a 450W unit, with two 6 pin supplementary power feeds.