Ive just started faffing about with Reaper after recomendations from Rhythm Tech a few months back, its really well laid out, nice clean graphics, simple enough to get your head round and like you say really low CPU use.

Ive never got on with Cubase and wouldnt ever use half its functionality anyway, I just wanted something nice and simple to work with and it definately gives you that.

Its free (ish) - full functionality if you dont pay, you just get a nag box every time you load it up or $50 for non-commercial use. Youve got nothing to lose downloading and playing about with it.