I own an Atomic AT 1600.1D and recently purchased a Sundown SAZ 1500D because I am converting once the Sundown 50.4 comes out. I tested it out today in my truck and here's my opinion. Both amps are very very well built. There was noo difference in bass and performance. Both amps never get hot. They both performed surperbly on my 3 10's. The major difference and Chris from DB R told me this was the heatsink design. The Sundown was much heavier. The Sundown is built like a tank I mean that "mother" is one solid amp. The external appearance for both looks about the same the Sundown in my opinon looks a little better. I think the major difference though will be in customer service, warranty and reputation. They obviously both use the best parts. It's just a matter of choice when it comes down to it. I like that Jacob has answered many of my questions, very knowledgable and seems to be a cool dude. The SAZ 1500D just seems to me to be a little bit better built. When you hold both amps in your hand you can tell the difference. The Sundown is built like an old style amplifier

Drop that sombitch to .35ohm and 18v for a burp and see which one is loud and which one burns up.