while talking about whats better I am going to be putting two 07 or 08 USAMPS MD.3D to Two JL 13w7 the specs are different from the Jl to th US from what I know. I hope the merlins sound good and hit hard on those jl subs.
I chose Sundown Audio, but from what I hear the MD2D is a solid amp. US Amps older stuff is was the best out there, but in my opinion the only thing I really like from US Amps are the AX series.
The Sundown SAZ 1500d will be more flexible if you make changes in the future also.
I'm an old school usamp user and installer. I still have a usa 150 and used to use a usa 400x. Recently put in 2 md1d's strapped together and this is the loudest system i've ever personally had. I love the new amps and consider them to be just as good as anything us amps has ever made.
Let it be known, us amps has made some changes in the past few years. But one thing has remained constant. Their outstanding engineer "Dirk" whom still designs and did design the AX and Merlin amps. I also had an AX1500DE and recently sold it before i got the 2 Merlins. I'm very impressed with the Merlin.