I'd not buy an AGM battery reading 12.3v. There is no Bargain there.
If these AGMS are going to be deeply cycled and not 100% recharged nearly every cycle, they will not be the best AGM for the application.
They are said to be, on some marine forums, very poor at PSOC cycling, partial state of charge cycling, losing capacity quickly and being very difficult to recover compared to other higher quality, higher$$ AGMS like Lifeline, Northstar and Odyssey.
The Member CMS in the following link, is well respected on every forum on which he participates, as he is a fountain of knowledge and experience and also writes clearly and concisely.
Look at post 49, where he speaks of the Deka AGM G-31 or the EP G-31.
EP meaning East Penn who make Deka intimidator.
http://www.trawlerforum.com/forums/s3/carbon-foam-batteries-1-year-later-26233-3.htmlHe says Deka themselves rate the their AGM at ONLY 350 cycles to 50% depth of discharge, less than half of Northstar or Odyssey and about 1/3 that of Lifeline.
If true, that bargain just got expensive.
Unless you can't recharge the batteries properly anyway, then just get the cheapest you can find and ring the 'works just fine' bell as long as you can.