You have hinted at your uses, but one big divider in my mind is whether you just want to make a few frames as you say, or whether you want to make frames to a professional aesthetic standard. I also feel, but don't have the chops to prove, that there is a possible level beyond pro, which is awesome combined with extreme cleanliness in welding. The level above that is to produce TIG art, and I have seen a few examples of that, and have a few ideas, though as I say, not there yet, by a long shot. So three levels; pro structure; pro clean; and pro art. To get to pro art, you have to have a very sophisticated welder, and in my mind it has to be an upper level Dynasty type processor, and I know other people who say that. At that level one is essentially painting with the arc, and more pallet is more options. Though, I have seen pro art, done with a transformer machine, he just said he could have taken it further if he had a Dynasty; and it just takes someone to make it happen with whatever...
Number 2 is the Aluminum thing. I went down that road once, and for me it was a bad choice. Aluminum is so useful that not being able to weld it was a mistake in my mind. Affected resale, I would not do it again.
With TIG, the number one name is miller. When I bought my first one I bought a Maxstar 150, which is. I bought the package that did not have HF, and Pulse. I was told the pulse was useless, and the HF was inferior to Lift arc which is true in an it came along second way, but not otherwise. Normally I go big, but on this occasion I saved a few bucks, and the result is I ended selling it and moving on.
Since my first buy there has been a huge improvement in the quality of the Chinese product. They make IPhones, they can make welders. When I bought about 10 years ago, the chinese inverters were not adequate for basic TIG, they were all scratch start machines. You are a pro welder, but most people can't even get to structural with that kind of machine. However, today, there are welders, that are nipping at the dynasties for a lot less money. I was set on a Dynasty, but there is one problem with them in the amateur shop. I need a machine that is guaranteed for life. I will take one with a realistic chance of lasting a lifetime. What I was hearing was that if you have a payback within the warranty, Dynasty is a good product. But here are 4 points:
1) Every time I visit my supplier, not even a welding store, an industrial supplier, there were several Dynasties/Max waiting for repair.
2) They have a reputation for things going wrong, and when they do they need major component replacement, it is a laptop, not a PC. I am not saying these inverters fail more often I am saying they fail, at some noticeable rate, and that they are expensive to fix if off warranty. My maxstar was fine.
3) I don't use a welder enough for several years of coverage to represent payback
4) There is at least one prominent claimed case in Canada, where I live, of Miller stonewalling a warranty claim on a Dynasty. They could have had a point, but the bottom line is the incident undermined my confidence the machine would even last me out the warranty period. I was confident it was unlikely there would be a problem, but not confident it would be dealt with. And beyond warranty...
None of this makes me feel Miller is bad, it just illustrates that amateur issues are different. One thing about my Miller was I did resell it and got about 66%, so my carry cost as an amateur was favourable.
What did I end up buying, in part because the guy who does their quality control is only an hour from my home:
These videos got my interest, and I looked into these machines. They have some pros and cons, the tipping point for me was that their quality guy is their Canadian dealer. He is in China all the time, and he is local around here. This meant the Canadian product had a better rep than the US, at the time. I really wouldn't recommend this route, I have not had enough time with the torch to tell you anything. I kinda ran out of money to make the upgrades I wanted to make, so I have not fully tested it. Stuff around here takes so long. All I am saying is they have upped their game, and sometime the economics of a small shop are different. For a lot of guys they are different on affordability, but I look at it differently. More like a business, but as an amateur, and the numbers are different for me.