It has been my experience that the best preamp is no preamp! I am currently using the output from my Geek Pulse directly into my tube monoblocks. The sound is the best I have ever had. BUT, I am almost 100% digital using my NAS drive and my music laptop into the Pulse. When I do play vinyl, it is to make a digital recording. I rarely play vinyl just to listen to it any more. My recording capability is so good that after I use Audacity to record and Click Repair to clean it up I have a wave file that in most respects sounds better than listening to the vinyl!
However, I can get away with this because of my choice to go completely digital. I only have one setup and that's the digital. You have several source components and I understand it is much easier to use a preamp to control what you listen to. In my case, if I want to listen to a record I have to rearrange two sets of interconnects... still not a big deal. For you with more sources that would be inconvenient.
I have always been impressed with Emotiva's well designed equipment and reasonable prices. You have a strong recommendation from David and he has lots of experience with the piece you are looking at. His advice also make sense to me!
The Marantz is a very well thought of unit and could be easily used in another system in your house or sold for a good price. It also has the benefit of having the preamp built in and therefore one less pair of interconnects is needed. Easy to use in a second or third system.
I agree with David's response. Go for it!