I have owned the 805's (two different pairs and vintages), the V12's, and the SixPacs outfitted with upgraded parts. And quite a number of other Cary amps to boot. :) "Sbank" offered some really sound (ugh) advice on the 805's -- they are NOT a good match for your speakers. Please don't infer that I'm bashing the 805's. Anything but, as they will likely go down in history as some of the best sounding amps of all time. BUT...they must be mated with a speaker load they can handle, and 87 dB sensitivity is too low. They need at least a 93 dB (preferably higher), and they need a fairly benign impedance load in the 8+ ohm range.
The V-12 would be a nice step up from the SixPacs, and won't put out any more heat (same total # of tubes). But before that, have you tried rolling any tubes? You didn't mention what brand of output tubes you're running. My favorite current production tube in the Six's was the Electro Harmonix EL-34, and my favorite NOS tubes were the GEC KT-66's. The latter are a bit price prohibitive right now, but the difference in sound over the EH's was substantial. I haven't tried any of the new manufacture GEC's, but they may be worth a look.
The V-12 would be a nice step up from the SixPacs, and won't put out any more heat (same total # of tubes). But before that, have you tried rolling any tubes? You didn't mention what brand of output tubes you're running. My favorite current production tube in the Six's was the Electro Harmonix EL-34, and my favorite NOS tubes were the GEC KT-66's. The latter are a bit price prohibitive right now, but the difference in sound over the EH's was substantial. I haven't tried any of the new manufacture GEC's, but they may be worth a look.