What's a good secondhand laptop for Ardour?

Hi all,

I’m starting to work on projects with higher track counts and more processing and need to think about a better computer (currently using an old AMD Athlon 64 x2).

Can anyone recommend a good low-end current laptop or (better yet) something I may be able to pick up used which would offer a chunk of additional DSP power?

My budget is $500 (less is better) and I use a Tascam US-800 (USB) interface with AVlinux, Ardour and Mixbus. Outstanding realtime performance is not a huge priority for me. Thanks!