What are you welding? I am welding auto body, frame work, jeep bumpers/suspension components, and misc projects (weld table, work benches, fixtures, artsy **** for the wife, etc). I have two machines. A Miller Thunderbolt - 150 amp DC / 225 amp AC stick welder and a Hobart Handler 187 - 185 amp MIG welder with shielding gas. I use the MIG for most anything up to 3/16" thick, it will do 5/16" but the stick welder does it better. I use the stick for everything else. Use .023 wire with 75/25 for auto body, .030 for everything else. Use 3/32 and 1/8 7018 for the thicker stuff. Can weld thicker stainless with the stick just by changing rod. The MIG is relegated to just steel as other metals cost much more in consumables and aluminum would need a spool gun.
I am restricted to just steel for the most part. For home use that hasn't been much of a problem. Aluminum is expensive to do it right. I am fortunate that I work in a fab shop, so aluminum projects get fit up at home and I have one of the welders weld it for me at lunch or after work. I honestly don't have a need to weld much aluminum though.
I suggest you buy quality single purpose machines and build up a collection. Good stick welders (assuming you don't own the tombstone you have) can be had on CL fairly cheap. A quality MIG welder can be had for around $900 by the time you get the machine, bottle of gas, and first roll of wire. There's a reason the cheap stuff is cheap.
Most of all, evaluate what you need to weld now and buy for that. Tomorrow will sort it's self. One day I will buy a TIG welder, when I have a need and the money is laying around. MIG is so much more user friendly, simple, and quicker than TIG.