I recently sold my Arc xdi1200.6 and replaced it with the Zapco ST-5x. Before anyone asks, I got rid of the Arc because the fan was pretty audible in shared cabin space. Just knowing that it was audible even when I couldn't hear it over the road noise and music was enough to drive me nuts. The new owner will be putting it in his tire well just like I had it for a few months and never heard it in there. But since it replaced a very well liked 6ch I'll do a comparison. First I'll hash out the meat and potatoes. The manual says it does 80x4 at 4 ohms and 350x1 at 2 ohms on the sub channel. All channels are class a/b including sub channel. Zapco's website states slightly different power ratings so someone I know at Attrend will be taking my very valid question about power specs straight to the horse's mouth. In real world I don't think it's a big deal.
The amp is built like a tank with good connections. It puts out good power and plenty for the front stage and sub in my siggy. In a direct swap I believe it sounds more transparent than the xdi even though the xdi put out a TON of power and seemed to be a little more dynamic. For an amp that goes for around $300 at full retail I don't think you can go wrong. If people that are used to high dollar a/b amps are saying these amps are the real deal they're worth a hard look. Noise floor is also lower with the Zapco. I'm putting serious thought into getting the 4ch that does 150ish x2 bridged to add a little more heat to my doors and running rears, tweets, and sub with the 5ch. Other than that I think my system will be "done" once I put the little 4ch in. Not sure who I'm trying to fool by saying "done" but I can only hope, lol.