been tig welding for 22 years here's my 2 cents, combination tigs are great (mig and tig or tig and plasma) but when one breaks you lose 2 tools while it's being fixed no tig or mig to use.
I've used everything from water cooled 700 amp kempi to $10000.00 ac/dc millers.
there are a few things to consider when looking for a tig no matter what size or brand ,look at the specs in particular the duty cycle the higher the number the better( you should be looking at atleast 90%) the lower the number the worse it will perform on an extened weld eg.. the amps will slowly drop the higher the number the less drop..
the best brands are esseti, caddy ,miller and kempi , here's my rule the more nobs and the more settings you have to play with only make for a bigger headache to get it right as these machines are never very forgiving if not set quite right pulsed tig is fantastic if you use it everyday and have the time to get set it right.the tig I have at home cost 300 bucks has 2 nobs on/off and amps and it works great i grind near it I've dropped it and I don't have to worry cause it did'nt cost me 2 grand,for any alu welding I need I just take to shop to have done (on that note most people don't realise that alot of migs can weld alu with few minor changes)having said all that crap tig welding is pretty easy to learn , it's not until your under the car and that blob of hot stuff has gone down your sleve and is rolling aroung your back that you find out how much fun it is..