Mello, there are not a lot of low power balanced amps out there. Our S-30 is likely one of the few, but it is a stereo amplifier, so you would have to accommodate that if that is how you proceeded. It might be easier to get some smaller amp since the tweeter only needs a couple of watts, and run the amp using half of the balanced signal, while loading the other half so that the balanced operation is maintained.
The midrange is going to need more power- 60 watts might actually be enough, depending on the room. As a side note, I would also try operating the tweeter off of the midrange amp, using an attenuator to reduce its level. You may find it sounds better- electronic crossovers often rob the system of detail.