HD space isnt a probelm, you can get a 250GB HD for stupid money!
Any idea what programs you will be using on it? meaning are there gonna any programs that require high CPU speed?
I suggest looking around and not going to any rip off stores like Dixons or PC world that charge over the top prices for PC's to punters that no nothing about them.
This is a site I use : click here
YOU choose what you want in a computer and they customly build it for you!