Dolby Atmos, ROTEL RSP-1576 and ROTEL multichannel amp suggestion

[Guybrush]

Since I saw the new RSP-1576 is coming out, I started thinking about adding Dolby Atmos to my 5.1 Magneplanar speakers home theatre. I just bought four BG Radia in ceiling speakers (to timbrically match my planar speakers) but I need an amplifier. I have a ROTEL RMB-1075 which drives my Magneplanar SMGc speakers, but now I need another amp (I would like to buy a used one). What would you suggest ? Two stereo amps ? A multichannel amp (like the one I have or the RMB-1048 or the RMB-1066) leaving some channels unused ?
This is the link to the speakers I bought:

http://bgradiadesign.com/product/rt-6-planar-in-wall-ceiling-speakers-pair/

Thank you very very much for any suggestion given.