Are XLR-to-USB preamps considered "interfaces" by Cubase?

I’m looking for a way to record vocals now that I’ve switched to using a MOTU 24I/O interface, which only has TRS line-level inputs. I thought I could just switch over to my MOTU UltraLite interface as needed (since it has two XLR pre inputs), but Cubase loses all of its input/output audio routings when I switch interfaces, including external instruments and effects.

I am prepared to just get a standard hardware preamp (currently looking at the ART Pro MPA II), but my 24I/O is already maxxed out and I don’t have any more rack space for another device.

I’m very interested in these XLR-to-USB preamps, like the Shure X2u, however I am concerned that in order to use them in Cubase I’d have to select them as an interface, which of course leaves me where I am now with the UltraLite.

Does anyone here use XLR-to-USB preamps, and if so, how do they integrate in Cubase? Can you use them alongside your primary interface? (I am on Windows, BTW.)

Generally, everything that is a mic preamp and is not standalone, but USB or firewire needs to be set as audio device in Cubase.