Sorry Sonic but what card are you contemplating buying? Also where did you come across that information regarding nVIDIA have extreme number-crunching power (is that compared to ATI)?
I only ask as I use both nVIDIA and ATI and both high end cards do exactly the same job in the same time. As for CPU's much the muchness when you go over 4 cores. 8 cores and you are really in the world of servers. Never confuse cores with threads. The big daddy is still the i7 9XX but AMD are releasing the Bulldozer platform shortly and I think it will be the one to watch. I spend most of my time over at Tech-PC forum.
http://www.tech-pc.co.uk/forum/
My day job is industrial CNC's (electronics) but for the past 20 years starting with the 386 I have built, sold and supported PC's as a hobby and as a job. When it comes to post processing it is important to remember that most people only deal with ~4 images open at a time (Lightroom will happy eat 1-4 gig of ram) 16GB is overkill IMO unless you are either video editing larger files or using it for VM's.
If you like small PC's then mine is not for you:
http://backup.cambridgeincolour.com/...4/pc004pc0.jpg
That is 35kg of PC and large. Case is a Kandalf LCS (Liquid cooling) I now have a larger screen as that was taken almost a year and a half ago. Internals have been chopped and changed since.