A reader pointed me to a thread on the NI forum in which folks have successfully gotten Guitar Rig 3 running on the super-cheap, super-small Eee PC from Asus. You’ll want to run Windows XP rather than Linux, and you need modded graphics drivers so you get a more-usable 1000×600 resolution, but it looks like it works pretty well. Of course, plenty of other laptops would do a better job, but the fact that it’s possible, and the Eee is as small and affordable as it is, is encouraging. (You could actually run Guitar Rig on Linux via WINE, but I think XP is an easier way to go.)

GR3 + Eee on NI Forums
More on the Eee: Asus Eee As Cheap, Tiny Music PC: Guitar Rig 3, Linux Tips on CDMusic.com

I have a healthy respect for dedicated audio hardware, but when it comes to digital, I love computers.