+1. Actually, I would just go directly to outboard amplification with the LSIs. Low sensitivity, low impedances, and IIRC they might have difficult phase angles to boot.
The easiest, and or cheapest, way to achieve the above would be to buy a midline 7.1 receiver that has preouts, and add, say, an Emotiva XPA3. Outboard amp channels for the LSIs, and the AVR will be plenty for the Speakercrafts.