Never having played with the sundown but having a md3d in my garage, and knowing many MANY peoples love for sundown here, i'd definitely suggest the sundown for the build quality not to mention that i've heard nightmares about warrantying an amp with US Amps. I personally had 2 md3d's rca inputs come apart and after sending it back to them twice, just glued it back together and ugly as it may seem, hasnt happened since. If you care about build quality, not to mention the support that comes with their customer service on here, go with sundown.