Which of the ZyXel devices seems to be the preferred model with members of this forum? The 8324-B10A, 8924-B10A or the 1312-B10A? Still doing my research on which to go for.
From my reading and understanding of the forum I'd say most people would recommend the 1312-B10A if you intend to use it in bridge mode as a modem only, and the 8924-B10A if you wish to use it as an all in one box.
All 3 you mention have the coveted BCM63168 chipset that seems produce the highest sync speeds on most lines. The 1312-B10A came out more recently than the other two, so even if purchasing from ebay you are likely to get a unit produced within the last year or so, but other than that its the least capable as a router, sporting only 100mbit ethernet ports and wireless N. The 8324 is similar but with gigabit lan ports and is an older model, so even "new" stock is likely to be old in comparison to the 1312, the same can be said for the 8924 but it has AC wireless.
With that said, all 3 are great candidates for using in bridge mode, and you might find the 8324 & 8924 to be cheaper.
Another option is the Billion 8800NL (R1 version), it has the same BCM63168 chipset and can be found for reasonable money.
Do you have another router you want to use with the modem MrMike?