It seems like the 3 Port is very linear in it's power band. It is not particularly strong in any part of the power range, so is easy to drive smoothly. I have not owned one, but this is what the guys who run them say.
Try the 7 mm restrictor in the 7 Port. I run the 7 mm in both my 5 and 7 port, and find they are still very economical with grunt to burn.