I had a Fireface 800 until from 2008 up until a couple months ago. I can't recommend highly enough, but my recording projects slowed down considerably and it was just too much interface. I sold it, bought the ur28m and pocketed the rest.
The Fireface UC might be a great option. USB connectivity, which is great since Firewire is dead, expandable to 18 ins and outs, has SPDIF connections, and has all the stability and quality you'd expect from RME. The only downside is that it costs about double the ur824.