Exchange a 1.5 years old super fast computer, dont think so.
The CD MBP is a very performing machine. If you dont do serious work like HD editing, Maya or play the last game, you will see none improvements.
You will just throw away 1000 usd. (upgrade price)
I have the same machine, I have made the question, Do I really need something faster?
Tiger will scream in this machine anyway. Is 32 and 64 bits optimized, not only 64 bits.
Do I use programs that need large memory blocks access , 4gb?
Nope.
So, I stay with my CD MBP.
my2cents