I would decide on three factors:
Room Correction Software. I know nothing about the Advanced EmoQ software that Emotiva uses, others may can comment on how well it works. The Marantz uses Audyssey MultEQ, which is not their most advanced, but a well known software. The NAD also uses Audyssey (the V3 uses Dirac). My vote is NAD or Marantz.
Features/Usability - You said you already have a Emotiva amp so the asthetics may favor Emotiva. You will have to see which ones have the features that are important to you.
Price. I know A4L has the Marantz (refurb) at a really attractive price. Emotiva has refurb units too, but at a couple hundred more.
Other than differences with the room correction software, I don't think you will hear a difference between any of them.
7.1.4 Theater Room (In Progress): JVC-RS46U, Silver Ticket AT 2.35:1 142”, Onkyo RZ830, Anthem PVA-7, Panasonic DBT-110, JBL Studio 270’s, 4 - 15" DIY Sealed Subs
3.1 Living Room: Samsung 64” F8500 Plasma, Anthem MRX 300, Dynaudio Audience 52’s, Dynaudio Audience 122C, NHT SubOne