Suggestions for a 4-port analog capture device, USB or PCIe?

[ConcreteRooster]

I recently moved into a house which came with four analog cameras (not sure of the make/model). The cameras are currently connected to a Speco DVR4RS. It works, but it seems kinda klunky. Plus, I already have a Linux server and a decent amount of Linux experience. Zoneminder looks like it might be an upgrade.

I need some kind of capture device. USB is preferable, as I'm out of PCIe slots on my motherboard. But I'm not opposed to building a new system as a dedicated ZoneMinder device, so PCIe is an option, if that's what it takes to get something stable and not outrageously priced.

The Sensoray 2255 looks ideal, except for the $500 price tag. (Explicit Linux support by the manufacturer is always nice.)

On the other hand there are shady-looking 4-way devices for $10 or less, but no mention of Linux support or even what chipset is used.

Seems like there ought to be a middle ground, but I'm having trouble finding it.

Thanks!