Not quite. Typo perhaps?
Two 4Ω loads in parallel is 2Ω, which a good amp should be able to cope with but is not best practice.
Two 4Ω loads in series would give you 8Ω, which may have allowed an easier match to suitable amps.
What you have though is 2 8Ω drivers, so your choices are: series wiring for 16Ω total as you initially described, or parallel wiring for 4Ω total.
Getting the most out of the drivers will be more expensive with the 16Ω option as that requires a bigger amp, so I'd recommend putting them in parallel for 4Ω nominal.
Assuming you pay attention to how hard you are driving them and don't simply thrash the living daylights out of the system, then traditionally we'd size the amp at 2x the nominal/AES rating of the speakers to maximise headroom. This is commonly referred to as "program power".
That means targeting 1600W per channel from the amp for each pair of 12s. The LabGruppen you mentioned is therefore rather underpowered.
The 1250W offered by the Linea 48M10 is not far off this (only -1dB), so is a reasonable match.
If cost is critical, the 750W of the 48M06 is only 2.2dB less, so while not technically getting the most out of your speakers, will not be likely to be noticed by most of your audience.
It's perfectly OK to run different parts of your system at different impedances across multichannel amps - this actually reduces the total load on the amp (compared with running all your 12's off one amp and all your DCX's off another smaller one for example).
A 48M10 therefore could certainly run both your DCX's on one pair of channels (vastly over powered, but you'll be able to turn those channels down and not have them work too hard), both your 2x12 low mid sections on another pair of channels, and have 4 channels available for your bass section. Depending on how many bass drivers you have and how they're loaded, this might still end up a little light on LF, as the PM90 (particularly the DCX464) are capable of a lot of output.
Re the DC Resistance you measured, the 8Ω version of the 12NDL76 should be about 5.3Ω per driver, so ~10.6Ω for the series pair (+ a tenth or 2 for wiring).
Your 7.4Ω seems a little low for that to be the pair, or a little high if you measured it individually. I'd re-check each driver individually to be sure that they're closer to the factory spec before applying any real power to them, just in case something's wrong.
HTH,
David.
