if you cut alumnum pipe, just use a regular miter saw. It cut pretty clean. Abrasive chop saws are not useful for aluminum pipe. Jigsaw can be use on aluminum sheet metal with great result too.

Btw, what kind of welder are you using. If possible, get a watercooled torch because it is so much lighter which give you more control over the torch. I have a standard torch right now which is pretty heavy at time and want to tilt out off angle when I weld.