why not use the SAME amount of money and buy a mac pro. They are way way faster then any macbook pro commin out.
Your 2008 mbp is still perfect for tracking and stuff.
Damn I use a 2006 mbp for mobile recordings without problems
I use a 2006 mb white plastic one to record. I simply installed a 7200rpm hd and it's enought with a 2.0gHz C2D to record stuff on 16 tracks or more!!!