The big mismatch that we see often with the BeePre is a very high power amplifier with very efficient speakers. This is completely eliminated if you purchase a power amplifier with input level trim controls.
The input impedance of the amplifier should be greater than 600 Ohms.
The RC-70's are a 92dB sensitive speaker with a couple of 4 Ohm dips. A 100W amplifier will produce enough SPL to drive you out of the room, and 50W is likely to still be an absurd amount of power. Putting a 300W amplifier on 92dB speakers would not be a good match, though you could use -12dB inline attenuators at the inputs of the power amp to mitigate the issues you'll face. I would personally go for a Gainclone until you find the next pair of speakers that you want. A gainclone should work nicely with the monitor speakers that you are interested in, and ought to be fine with those transmission line towers also in a room that isn't too big.