Are the current lineup of Merlin US Amps strapable?

[Hayabusa 0]

My cousin has a MD2D that he got earlier this year on his 4 12s and was wondering if he added another MD2D or MD3D could he strap it with his pre-existing MD2D? If so does he need some thing that I heard about a few years ago called MLT or does he just need another set of RCA jacks or something or is it even possible to begin with?

[USAMPFREAK 4]

Have him give me a call I will talk him through the set up.