I am in the same boat.
I got a job using Adobe Illustrator cs5 and Adobe Photoshop cs5 (64 bit).
I was looking around and I asked my grandfather (builds computers)
Specs include...
i7 processor
8GB memory
500MB - 1TB hard drive
High screen resolution
Screen size from 14-17"
Prices ran from $500-1,500
I just ordered an Intel with all the specs listed for $599 + tax.
I hope this helps.
BTW, I do graphic design for ink and vinyl printing on all clothing, mainly shirts.