Flash disk and ram upgrade or you can fit in 2 disk instead of one
Any store will do although those apple authorised might charge you more

This post has been edited by viper-xs: Feb 6 2011, 04:15 PM

Rendering etc is not my field but I'll try my best in terms of sharing friends' knowledge in this area.
From what I can remember there are few that you can do to improve it. Sunce this is mbp you can forget about those cpu, gpu and stuff. If you have a friend that can lend you these spares before deciding then it will be great. Upgrade ram to 8gb and try to get perhaps a firewire external disk for you scratch drive etc seperated from the OS. If you see performance gain noticeably faster then you can think of maybe:
Getting firewire external drive
Get a second internal hdd and decide for flash or those normal ones
For memory you can try to install some freeware and when you do your rendering please watch for some vital stats like swapping etc. This will pretty much tell you if you are in need of memory upgrade

I won't suggest new mbp since you still limit yourself in terms of these. If you are serious might as well go for mac pro or maybe imac the very least. You waited for new mbp and adobe released new software that basically tie you down again. If you want to make the best experience out of this then maybe try those upgrades. Can always carry the ram perhaps or sell it off and certainly move the flash disk or ext fw hdd to new mbp should you decide to get one