OP didn't mention anything about rendering?
Do you mean encoding, I'd expect video editing these days will be using HD codecs so probably doesn't need to encode from one format to another.
To be honest, when people say 'video editting' they are being a bit vague. Depends on what you are actually doing. Simply importing camcorder footage, cutting pieces out and adding a new transitions are all fair low end spec requirements.
Uncompressed video to HD codec encoding requires a good CPU, adding special effects requires lots of RAM etc etc