I'm thinking about buying a Tig machine. I'd like to be able to do chromoly and some aluminium fab work. What should I look for, in the machine? What are the most important feature's I should look for? There's a ton of machine's out there, and I could use some sound advice. I don't want to buy, and then regret not spending a little extra. Also, what should I expect to spend. Keep in mind, it doesn't need to be a production machine. Any help will be greatly appreciated.