The only experience I've had with electric impacts is the cheap $70 one I got from harbor freight. It was 270ft*lbs. it was good for changing tires but not much else. I am not sure about the upper end electrics, and I hope someone will chime in on those.

I have a 20gal compressor and a Chicago Pneumatic 800ft*lbs titanium air gun. The thing is MUCH smaller than any electric i've seen, and only weighs like 8lbs. And it revs MUCH higher than the electric gun I have, which helps many times such as when you're undoing a ball joint nut and the ball joint stud spins with the nut. You put the gun on it and it'll spin the nut off the stud so fast the stud doesn't have a chance to spin.

Not to mention the 800ft*lbs that undoes almost anything, although being from new england I still break out the 4ft pipe "godzilla" if something is rusted too bad.

I beleive my gun was $230 and the tank about the same. I'd say for <$500 you could have a nice air setup. Of course I bought one of the best guns.. you could save a lot of money by getting a less expensive 500ft*lbs gun of good quality for example.

An electric gun may work dandy for you.. hopefully someone will give input on those. I use my cheap electric when I'm just changing tires and dont want to charge up my air tank.

-Scerb