zlone,
I have been looking for a doubling of wattage also, but thought that perhaps the 150/270 spec on the M5si might be enough. The specs on this amp also mention "512W peaks into 2 ohms", although I'm not exactly sure what that means regarding stability.
A complete doubling of power from 8 ohm to 4 ohm is a bit harder to find in integrated amps, as opposed to a separate power amp, but I was hoping to find an integrated that would do the job (hopefully at max $2500) just due to limited shelf space (and budget).
If I run across an integrated amp that is rated at 100/200, would that be a better bet than the 150/275 of the M5si? Or perhaps that all depends on the design of the particular amp.
Greg