Hi Mr Pippy.
The quick answers are
Windows XP 32 can only address a max of 4 Gigs of RAM provided you use the 3 gig switch in the start up ini. Which means that 4 gig of your RAM is doing nothing but consume power.
The quad core is fine and will get used under XP Service pack 3.
Win 7 appears to be a better option though I am still running XP 32 Bit so my knowledge ends there.
Your Laptop I would suggest a large screen, make sure the Firewire card is a TI card.
Others will give more succinct answers I am sure.