You have a small mill with a limited budget. If I were you, I would consider the Tormach Superfly that uses a single insert. Tormach came up with it as an alternative to their face mills when used on a low HP mill. It works quite well with a 1HP motor, can do a surprising amount of stock reduction and finishes better than their 38mm face mill. Inserts are pretty cheap and last quite some time in a hobby shop. I've done a 0.070" deep pass with that thing and it left a more than acceptable finish.