Harko,
MIG Welder - i recently bought a MigOMag and I think it's pretty good. 15kg wire, 6 broad amp settings, sire speed, burn back, spot and stictch weld control, Binzel torch.. feels really pro. twin cooling fans etc.. only draw back is quite pricey.. around $1600
can do up to 6mm.
http://www.migomag.com.auHad a go of a UniMig last weekend, and found it sucky, cheap torch, settings werent on a dial so you couldnt see the set up at a glance.
compressors, aplace called Buttsworth engineering had good deals on 17cfm units, but not quite the 3 cyl slow revver u had in mind i think..
try going to auctions for cheap trades tools.
Go the MigOMag!
Ed