Hi Phaelon,
I'm surprised to hear that you felt the VivA Solista sounded like it was "straining" to deliver the goods. My speakers (Hansen Prince V2s) are not as efficient as your JM Labs (87dB vs. 91.5dB), and I drove them to appropriately loud levels without a hint of them running out of steam.... I was so impressed with the VivA Solista's performance that I actually called the dealer late on a Friday evening to pass along my elation! Perhaps your cables had something to do with what you were hearing?!?