Avast has a very very low resource demand, exspecialy compared to McAfee and Nortan, i have a 450 MHZ CPU and 256 ram and avast set to high and i don’t notice a thing.
Before this i used a 200 MHZ CPU and 128 RAM and i still didn’t notice a difference when avast was turned to high.

So i would say that you are fine with the resource usage from avast!

EDIT: Sorry nearly forgot to Welcome you.

Welcome to the Avast forums merf

–Lee