to me there's 3 good welder brands
Miller
Lincoln Electric
Hobart
Hobartwelders.com is great as they have a message board and they all know their stuff. The Hobart units are more for hobby use but will get the job done
the Millers are more a heavy duty type unit and I trust them as i own a millermatic 175 175A 220V MIG unit from them
with your current welder you will need a teflon liner, you'll have to figure out a way to plumb the thing for shielding gas if its not done so already, and you'll need to keep your mig cable as straight as possible or the wire will "bird nest" at the drive rollers....it will happen often even with the cord straight...its just the filler wire is too soft to get pushed though the 10-12' liner
if your welder does not have lines for shielding gas your best bet is to either get a millermatic 175 and get the upgrade kit for the spool gun or get the better millermatic 210
if you can use gas remember to switch polarity for solid wire
i remember the day i switched from flux core to solid....just amazing and smooth running
Low price welding a metal fabrication:
www.freewebs.com/weldman
and check out my ebay items
http://search.ebay.com/_W0QQfgtpZ1QQfrppZ25QQsassZmoody07748
(updates every sunday night)