Hooking up Pre/Pro and Tube pre amp

I have my pre/pre (Anthem AVM 20) connected to my power amp via balanced interconnects (the power amp also has rca inputs). I'd like to hook up a tube pre-amp for 2-channel music, using the same power amp (Anthem MCA 50). Any reason why i can't hook up the tube preamp to the RCA inputs on the power amp (provided I don't have the preamp turned on when watching a movie or something)?

Is there a better way to hook up a tube preamp without having to run it through the pre/pro?

I too have an Anthem AVM 20 and run the front left and right interconnects through my Rowland preamp via the unity gain passthrough and out to my Classe' monoblocs. If your pre-amp has that capability do it that way.
That being said, you certainly can hook up the tube pre-amp to the RCA inputs on the power amp. Just use one source of input at a time into the power amp.
I have an AVM 2 used in HT and 2 channel. I would run the CD to the tube preamp and then the preamp to the direct inputs (5 or six channels available for direct DVD inputs but works fine for any analog signal) on the AVM 20.

That way you bypass all the circuits in the AVM 20 except the volume control and take the direct input from the tube pre to through the AVM and to the amp.

You simply select direct input on the AVM 20 when you want 2 channel and if the tube pre does not have a remote the AVM 20 volume control works for this. YOu do not need the extra set of cables to your amp.
Thanks for the advice guys. I'm seriously considering a Prima Luna Prologue 3 pre amp (just gotta convince the wife--this close to the holidays, maybe it'll take a couple of well chosen Christmas Carols ; )