I agree with "L" on waiting to do your machine shopping until later...take a test run on a few different machines and you will be able to get past the saleman trying to pass off the latest and greatest machine with a new knob to twist. When it comes to welding with wire welders, there are two knobs of importance...you need to be able to control your voltage and your wire feed speed....all other buttons and gadgets are just fluff to add and raise the cost of the machine. Many of the lower end machines cheap out to keep costs down and use voltage "selection" knobs where there are only a few voltage settings to choose from vs an infinitely adjustable voltage knob. These coarse voltage settings are OK, but having more control over the voltage is a huge plus, especially when just starting out. I find new welders fumbling with the settings and not understanding what the problem is or how to adjust the machine to correct it. Too much spatter and you'll find the voltage is most likey too low for the amount of wire feed speed. The wire is jamming into the puddle and splashing out vs melting off and becoming part of the puddle. Too much voltage for the wire feed speed will cause the wire to burn off back up inside the contact tip. Think of your voltage control as a way to adjust your arc length for a given wire feed speed. You will find alot of bad publicity on several welding forums given to FCAW wires, particularly the self-sheilded FCAW wires....not all of it is true, some of it is because the person with the gripe doesn't understand FCAW welding or their machine and how to correct the problem they are having. I find this to be true on car building forums.

Edit* I didn't mention ESO(electrical stick out) This is the amount of wire sticking out, measured from the work piece to the end of the contact tip(not the nozzle). This dimension is critical to adjusting your machine. If you get do not keep this stickout dimension constant, you will chase your machine settings all over the place. When the stick out gets too far out it is like lowering your voltage setting and visa versa. Also get the wire mfg's data sheet on every diameter wire that you purchase. This has typical settings on it to get you very close to where you need to be, and then you can fine tune your machine to get good results. Without this data, it can be a guessing game as to where to start with your machine settings.

Just my opinion, but just talking steel- there is a huge difference between gluing some sheet metal together and welding 1/4'' material adequately. Once you bring aluminum into the mix, I don't think the HF machine is the way to go, even for a "hobbyist".

Do yourself a favor and look on Craigslist for a name brand welding machine. There is a reason why HF welders are not used in professional shops. I have seen many Lincoln Miller Hobart machines for sale on Craigslist that are in your price range.