Just wanted to share this tip I derived out of pure frustration!
I'm busy with my March challenge project and so far have 14 tracks laid down. I find I have to adjust buffer size to avoid the snap, crackle and pop syndrome between recording/playback.
So I mixed down the 14 tracks to mp3 - yes, MP3
I named it "The mix so far" and then imported it as an audio file.
Soloing this track means the other 14 tracks and all their effects are muted. CPU usage dropped from 15 to 3 percent and I don't have any nasty side effects. It also times perfectly when recording a new track.
Come to think of it, you could maybe mix down your "basic" tracks - say drums, rhythm and bass and use those as your reference track when tracking a new one. Of course, once the project is completed, you simply delete this reference track.