I have been using my RME Babyface Pro for almost a year now, and while I love it, the number of inputs built in are kind of limited. I started looking at ADAT mic pres, which are not cheap and then I found out I could actually setup my old Saffire Pro 40 in standalone mode and use it as an ADAT mic pre setup for another 8 ins and out.
So I dug out my older MacBook (which was still compatible with the Saffire), ordered a couple of optical cables, and now I have many more inputs.

I don't really need the extra 8 outs, *but* it could be useful if I ever want to re-amp anything, and I also wanted to use the RME clock instead of the Saffire. Not that the Saffire is bad, but the RME is better.
As to why I need so many inputs.... well, I am lazy and I like to keep everything hooked up. Also, when I get inspired, I want to be able to just fire up Logic and hit record, I don't want to mess with hooking up cables. And finally, it let's me record a heap of tracks off the guitar at once, even if I don't use them.
The way I am set up right now I can record the amp track with IR, amp track without IR, fx track(s), and even dry signal for reamping later. Not that I have ever actually used any of those extra tracks, but I feel better knowing I can. And I also have my mics for voice and violin always connected, as well as bass and electric violin. So sweet!
Anyway, if you need more inputs and outputs for anything, and have an interface that supports ADAT, the older Focusrite stuff is well worth looking at for the price. It's hard to beat 8 pre-amps and 8 outs for around $100 or so.