if you get a warranty with the refurb then you can get that for 550 and not worry about a sketchy person on here stealing your money but on the other hand if you find someone on here with good rep and lives close to you, you can go and pick it up. Either way the kx I think are still more exspensive then the zx and people argue that it's worth it cause it's 1 ohm stable and does 2500 watts at 1 ohm but if you have the electrical to support the zx then you can run it at 1 ohm and do prolly 3000 watts although it is only rated for 2500 watts at 2 ohms. So I would go with the zx personally. I have one and I love it.