Thanks for your input, Mark. I was afraid this was what you would say.

It's something I should have made sure of, but frankly it's also something that should be better presented. There's absolutely nothing on the Amazon page that mentions that 80Mbps limit, and given the speeds that providers are offering these days, I don't think it's unreasonable to expect better performance.

But I'm also at fault. Now I know about this issue, and I'll design around it. It looks like I'm going to have to split this building up into a few different networks, one on each modem (they're also crappy routers, of course). They don't need to talk to each other at all, so it's not a big deal...