Snagged a Focusrite Saffire Pro 24 DSP at Guitar Center Hollywood this afternoon. Exactly what I wanted and little bit more. Free Bass Station VI included and an intro level to Ableton with an upgrade path. I'll look at it but DP is a permanent fixture for me.
Plug and play. The CD installer even requested to download the latest drivers, saving me from installing and updating later. The control software is excellent. Smooth. Easy, Flexible. Not only can you attenuate the Mac audio, but apparently various routings, which is really cool. Some very nice unexpected features, like adding reverb temporarily to the mix (with separate channel controls), Gate, EQ, Compression, and the odd but very useful ability to hear the mix in different listening conditions, such as from a TV speaker, bedroom clock radio, home theater, various studio speakers, and a bunch of other options. Doesn't sound like much, but very useful when writing for TV and wanting to know what you're going to sound like on NPR at 6:00 AM on a Bose Waveradio.
I have to see what all that means and how to make all that work but that's what long weekends are for.

Thank you one and all for your input and suggestions.