Running those applications takes minimal CPU and GPU power. I do suggest and advocate going for the best screen and keyboard you can get as these are the primary interfaces with the operator and define the user experience.

Greatly increasing the power of the CPU and GPU can make things snappier and smoother but you don't feel the difference like improving the monitor and keyboard. The only hardware improvement that comes close is increasing the available RAM. Ram is so cheap now there is no reason not to pack it in. Limited only by the OS, MB and your wallet.

For me a 19" screen and AT 'clicky' keyboard are ante to get in the game. I can work with less but won't be happy doing it. I plan on upgrading my unit soon and have a sweet old-school keyboard and 24" monitor picked out.