Do you live near Durban?
Coz if you do : BUY EVERYTHING from zones. They're by far the cheapest shop in SA.
The MOST important thing about your R13000 pc would be the screen, don't try and save money there...
22" is simply awesome.
On the mouse subject :
Gaming mice have more buttons!
You do even get wireless "gaming mice" like Logitech's G7, I know a few guys that play online COD4 with it, but I know only one that likes it... But remember to get a nice mousepad as well, you don't want to waste a good mouse on a crappy wood surface etc.
A wireless mouse has got a teeenie weenie delay in response time, and is too heavy
The CPU/RAM/GPU I mentioned should be fine if you're not planning to overclock. If you are, just swap the RAM out for 2x2GB OCZ SLi edition RAM @ landmarkpc.co.za, it'll be R1600 instead of R800 for 2x2GB.