Personally, I'd look into a solution with more amplifiers. It seems a bit of a waste to spend money on "high power" 6-channel amplifier, then use two channels to power your tweeters. I'd look into using a cheaper relatively low power 4-channel amplifier to power mid-range and tweeters, and use something bigger to power the mid-bass, or a relatively high wattage 4-channel amp could power the midbass and also subwoofer with the other two channels. Alternatively, you can go with a 4-channel amp to power mids and mid-bass, and throw in a cheap 2-channel amplifier to power tweeters (e.g. Boston Acoustics GT-275, if they're still sold). Wiring and fusing the wires can get a bit messy. However, if the complete system could be built with just three devices (2 amps + DSP, or just three amps), I'd take this route. Wiring and fusing for three devices should not be too bad. Take a look at the fused 3-way power distribution blocks from knu.
PS: Also take a look at SoundStream STL6.620. Two channels are rated 2x100watts RMS, and the other four are 4x60watt RMS. I have seen a test that showed that the test amp provided more like 4x70watts + 2x 130watts (all at 4ohm).