With those relatively large speakers (very nice speakers) that you have I would assume your room is not going to be small. Combined with a full complement of 4 and 6 ohm speakers with sensitivities in the range of 85 to 90 dB 2.83V @ 1 meter, the only receivers that can handle them reasonably well at -15 are the likes of Denon AVR-5805, 5308, Yamaha RX-Z11, may be even the NADT785. If I were to use my AVR-3310 and affordable amps to feed so many large mouths I would go with something like:
XPA-2 for the L/R (to get optimum performance and headroom for 2ch classical music enjoyment).
XPA-5 for the rest (people who listen to 7ch stereo at 0 may need more)
Crossover at 60 Hz
I would have never expected the little 3310 to do anything for your impressive speaker set up. What I find amazing is when people tell people to get an external power amp just because those little speakers are 4 ohm rated. When I see those posts I felt compel to caution them of overpowering those small speakers (e.g. HTIAB type) with affordable power amps such as the EMO XPA-5.