Miller welders are Good!!! I have the synchrowave 250 and its a superlative piece of equipment , however it cannot tig weld aluminum I should know as I purchased it to mig weld aluminum
and tig stainless /mild steel /general stick welding/.If you have the bent to mig weld the aluminum /magnesium alloys you will need a more specialised welding machine,ie something that
can break through the surface oxides and yes they are still there no matter how well you clean the weld area.so we go to
high frequency overlays on the base welding current,this AC addition to the base welding current allows the formation of a controllable weld pool and as fellows before me have said is very similar to oxy/ acetylene welding , its the only way to go for the aluminum alloys great for piping and small assemblys where the finished look is crucial .One drawback is ,like oxy welding there is a huge heat
build up on either side of the weld which tends to major distortion in welding panels.for most purposes a mig welder with a time adjustment for the weld period would suit you just fine
as you could also use it as a spot welder to stitch panels into place with minimal surface distortion ,The syncrowave 250 will set you back somewhere between 3500-4700 depending on the add ons you want .If all you need is a good welder for your home projects I suggest you go with the 150 amp version and
save acouple of thousand *last jan I bought a new tig welder
(miller) for one project ($1600) and since then have used it
exclusively for stick welding (a basic AC/DC welder with a foot
control to regulate the overlay A/C frequency in tig mode)
I could have done better buying smaller tips for the mig and a couple of boxes of smaller wire,would have saved me some 1200
green ones