In terms of specification if it says Intel Core Duo and has at least 2 gig of RAM it will do you a decent job. There's no point going past 3 gig with 32 bit XP or Vista.

After that start point you are going to pay for disc space, branding and graphics capability.

If you aren't processing video or uncompressed audio (wave) files then you will not run out of disc space.

A larger than normal graphics resolution (1400 x 900 perhaps) will make life easier when editing, but I'd look at a larger screen size (17" wide?) to match; high res on a small screen can be a recipe for eye strain (with eyes my age anyhow) might be better to invest in a big LCD instead.

Unless you are going to run games then the basic graphics chipset on the laptop will be adequate. If you are going to run games, especially anything recent, the cost of a notebook with sufficient graphics capability can get amazingly high.

Whilst I'm not a laptop user myself I'd take a lot of persuading not to get a Sony or Lenovo.