I'm upgrading my home studio and I'd appreciate advice on
any options I should consider for the following:

I have a computer based sequencing/audio/recording setup on a
Mac, but no audio interface for it yet. I've also outgrown
my current mixer. So I need an audio interface and/or a
mixer. Here are my needs:

1. I have 4 or 5 hardware synths with S/PDIF outputs. It'd be
nice to capture their digital outputs, but using their analog
outputs is also possible.

2. I have 2 or 3 older synths with only analog outputs.

3. At present I need only 1 or 2 mic inputs. Everything else
(at this point) is from a sequenced synth.

4. In principle, I can get by with just a single stereo in and
out on the computer interface and a good analog mixer. That would
probably be the cheapest and most traditional option. Sequenced tracks can
be recorded to audio one at a time and then mixed down on the computer.

It'd be much more convenient though to have a mixer or audio interface
that interfaced directly to the computer, so I could manipulate the
sequenced tracks on external hardware synths individually without having
to record them to audio. I'm thinking of either a mixer with a firewire
or USB interface, or a fancy audio interface that can serve as a mixer.

5. I figure I need at least 16 channels on the mixer -- at least
12 for the hardware synths, at least 2 for mic inputs, and at least
2 from the computer. 20 channels or more would be safer.

6. If I go with a fancy audio interface, I'd prefer one that can
serve as a standalone mixer, because I'd like to be able to play
without firing up my Mac.

7. I prefer a rack mountable mixer, because of the way my space is
arranged. That seems to limit me to 20 channels, I think, if I use
a traditional analogue mixer.

Some options I've come across:
A. Behringer makes some really, really inexpensive mixers with a lot of
features. However, I have a Behringer UB1622FX-PRO right now whose
sound quality is unacceptable (and actually appalling), so I'll need
to be convinced that Behringer makes good equipment.

B. The Allen and Heath MixWizard WZ 20:8:2 is a 20 channel rack
mountable analog mixer with a lot of features. It'd probably give
good audio quality and a good number of inputs.

C. The Yamaha 01x looks quite interesting. Unfortunately, not rack
mountable, but its other features may make up for that.

D. A MOTU interface like the 2408mk3.

Unfortunately, none of these options seems to have more than
2 S/PDIF inputs.