Again, if it’s a Mac you can easily aggregate (combine) several audio interfaces to one big interface which gets the same latency as the “worst” interface of the combined ones. For myself, I have combined a RME UCX firewire interface with the Quad Cortex USB interface and the latter turns up as 8 additional audio I/O channels in the Mac (for DAW and other uses). Roundtrip latency is 7ms (same as the Quad Cortex introduce).
On PC/Win I know that ASIO4ALL can combine audio cards but from what I’ve heard from users it introduces more latency and that it can’t compensate for clock discrepancy (which Core Audio does).