witch computer will you buy?

Hi

I will like to ask those people who got experience with after effects and many diferents equipments

Im learning AE I must say that is quite exiting but
last days I get stock on rendering and all that staff...

If you want to buy a computer fast to see the previsualizations
and good for render what you will buy?
MAC or PC and witch models
I mean I want something good but not something expensive...
Im using now a macbook pro with 4 Gb RAM and 2.4 GHz intel core 2 duo
I like the easy way to make effects on MAC ... but I dont know

any comments

Gerardo

learning after effects