The thing about RME is that their drivers seem more stable than others - probably because
they write them themselves rather than relying on third party chipset manufacturers to
write them. I'd maybe think about a Babyface partnered with an 8 channel A/D and D/A. A
Behringer ADA8000 would get you started for not much money and there are a whole host of
alternative analogue to ADAT routes.
The reason that many of these things have
mic inputs is that they're really cheap to add. The expensive bits like the case,
connectors and power supply are already there so a mic preamp only adds a couple of quid
to the build cost.
JRP Music - Audio Mastering and Restoration.