I just noticed that the OP was looking for thoughts on a sleep system for a COUPLE, and this is exactly what we have, the Hyperlite Duo and the Accomplice.
THIS IS THE BEST SLEEP SYSTEM WE'VE EVER USED, BY FAR!
Sorry for the shouting, but I just cannot say enough good things about this setup. This is assuming you are "cuddlers" like my wife and I are. Some couples like their own space.
One negative: the original accomplice we got (20 deg) was a bit thin in down in the torso area, hence I don't think it was a true 20 degree bag. So I added 2.5 or so ounces of down. Very easy to do yourself, one small slit and a 1" diameter, 1 foot long piece of PVC pipe and a piece of 3/4" dowel rod to "plunge" the down in (you can reach all the torso area chambers from the one slit), then finally a small piece of Tenacious Tape to repair the slit, and you're done. If you want more details, I can provide.
Anyway, last spring on the AT we did have one 5 degree night, and together with a couple hot water bottles and wearing our UL down jackets to bed, we were plenty comfy in our 20 degree setup.