Onkyo TX-NR807 receiver or similar - amp any good?

Hi I just got this aforementioned Onkyo receiver for my new home theater setup and I am also setting up my stereo with it - I used to have TV and stereo in different spots. I have some Vienna Acoustics Mozart speakers for the main speakers. On my old stereo setup I had some Marantz MA500 amps that I liked a lot. But, I only had two of them. Right now I am just using the Onkyo's internal amp for stereo listening. Since the Onkyo can run as a preamp only I, could use my two Marantz amps to amplify the two front channels on the Onkyo, but before I tested that out I wondered what the opinions are on the quality of the Onkyo internal amp compared to my Marantz amps? Also if I did hook the Marantz amps up it could be strange to have one kind of amp driving the mains and another for the other speakers in my HT setup - ? So maybe I should either just use the Onkyo for amplification or get some more MA500's?

Scott