I don't know if the 770's weight can be considered a "con" unless you need to move it -- it's about 15 pounds heavier than Outlaw's Model 750 5-channel amp (the 750 is 73 lbs, the 770 will reportedly be 87 lbs). By way of comparison, Parasound's THX-approved 220Wx5 amp (HCA-2205) is 85 lbs, the B&K AV6125 (125Wx6) is 43 lbs, the Classe CAV-150 (150Wx6) is 70 lbs, and the Adcom GFA-7500 (150Wx5) is 56 lbs. Judging from the Model 750, I wouldn't worry too much about the power supply being undersized.
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Gonk