IMHO i would get a 2x12 and wire two 8 ohm speakers in series for 16 ohm load and run it that way, instead of an 8 ohm parallel 2x16 or a total 4 ohm parallel 2x8 single 1x12's
if the 2x12 is closed back you wont notice much low end difference especially at low volumes.
as for the power amplifier, if it is mono-block capable and the power rated is 200W in mono (100W stereo) then yes, you will overpower a single V30 in mono mode for sure and could overheat two V30's on each side of that poweramp if you ran it wide open (100W into 70W speaker stereo L and stereo R - each speaker on each side of the poweramplifier)
but since the application is for low volume only and thats the whole reason you sold or want to sell your 5150 III, i doubt you will have a problem doing what you want to do no matter the setup you go with. you wont be cranking it loud enough to matter. you might get to 30W of the 100WL/R potential of that poweramplifier.
if you use two V30's in series you double the wattage capability of your speakers by dividing the wattage output in half, so you go from 70 to 140W capability, which is more manageable. so in the future you could get a 4x12, wire it stereo, and therefore it would be safe to use that poweramplifier with those speakers without worry of frying coils and having a matched setup. the only problem you might have there is overheating the poweramp cranked wide open, but again this is a low volume setup you want so i doubt you will ever have such problems.
