if cutting using the method Gabel suggests, by scoring the top and bottom lines with the circular and scoring in between, then banging out the waste and finishing with a sharp(if not sharp, add another ten minutes) chisel, you should be done in 10 minutes or less(pine). I like what Gabel says about the hand tools just get faster as you become more comfortable with them, I would add that they also give you more and more fun.
if you want to remove waste fast by hand, you need something like an adze or an axe that you can swing like a baseball bat. I hit the timber quite hard when working strickly by hand in our courses.

I meant a 1/2 or 3/4 diameter bit... we were working through a 1" deep blind housing in about 3 passes, so a depth of 1/4 to 1/2.
I'm sure you could go faster with more hp, just be ready to hang on tight. no trouble with level on the 1/2" bit, and the inside of the housing is unseen anyways.
Daiku did some posts on a very cool router jig that he made... you should search it out, there are some good pics.