I have a Lincoln Electric Precision TIG 185, and love it. (As well as a smaller MIG, and a large plasma). If you are doing the occasional aluminum, I highly reccomend the TIG over a MIG, if you are patent.
TIG is not quick.
I also use this as a Stick welding power source for heavier stuff, but in multiple passes, i've TIG'd 1/2" mild steel with this machine.
It is a transformer machine, so it is a bit heavier, and a bit more power hungary.
I have tried aluminum with both MIG and Stick, it ain't pretty.
You could also look into an all in one machine, there are a few offered by Lincoln Electric. I would stick to the two biggest companys, Lincoln Electric, and Miller.
With TIG, you can weld any weldable metal. Brass, Aluminum, Steels, Titanium, etc.
What sort of budget did you have in mind? What sort of work? Would you ever want to do anything outside of the shop?
Not trying to endorse it, but I do own a small welding forum, you can email me if you want the adress to get some more opinions.
Email is cam*at*weldingwiki.com (gives you a hint as to the adress of the site.)