The results are in..

In order of preference :

1. Neve 8816
2. Dangerous D-Box
3. Audient Sumo
4. Phoenix Nicerizer

The Neve's got it won on features and sound for me.
In terms of sound, it gives the low end a slight, smooth lift to my ears. It also rolls off the high end just slightly in a pretty pleasant way. It's kind of an overall rounding/warming sound I suppose.
Monitor control of two seperate pairs of speakers, talkback, heaphones etc.
With all that and the fact that it's got real knobs for volume and pan on each of the 16 channels (plus solo and mute) it does just about the best job of convincing me that I still have room for a real analog desk.
Unfortunately, because all its useful i/o is on D-sub, that means I'll probably have to put together a mini patchbay to interface my outboard with the 8816 - which is kinda one of the more compelling side effects of getting out of the box, however temporarily.
The 'width' control is like nicotine - just a little bit couldn't hurt, right?
Stuff like that always gives me the creeps.. "it sounds better - there must be something wrong", is all I can think. It's fun though.
Did I mention that this has the loudest headphone amp I've ever heard?
It does.
And the recall is a big plus.
I did try beating the shit out of the output stage (of course I did) by hitting it with a load of level on every channel. That sounded a bit more.. something. It definitely rounded off the transients a bit. Add in your favourite audio review adjective here. It sounded like that.
Although a little too much.
The long and short is that you can take it from clean to spongy depending on your input levels.

The D-Box I like a lot, mostly because it's got pretty much all the features of the 8816, apart from the fact that it only sums 8 channels and doesn't have the volume/pan knobs. It really does squeeze a lot in for your €1300ish. Sound wise, it's pretty clean and gives you back what you put in to it apart from the added depth and width the summing brings. The monitoring section is cool (nice knobs) and the headphone outputs sound good.
Unfortunately, I didn't manage to get hold of an AES to optical/spdif cable, so I can't tell you how the D/A sounds, but every report I've heard says that it stands up pretty well.

The Sumo is similar to the D-Box in terms of price, and pretty close in terms of sound, too. It had a very slight lift in the high end that some folks might enjoy, but I felt it kinda fell in between two stools a bit. It's not quite clean enough to give you back what you put in, but what little 'colour' it does add wasn't my cup of tea.
Still, it's got plenty of features, although I couldn't see myself using the bus compressor/limiter all that often.
The knobs are kinda mangy too. Am I shallow?

The Nicerizer, funnily enough, does sound pretty nice.
It's got a more overtly coloured sound, I found it lent a kind of tasty midrange crunchiness to some mixes I ran through it, particluarly a drum machine+synth heavy mix. Nice sounding unit, but I discounted it pretty early, because of its lack of monitoring facilities.
It does have a monitoring output, but it's just a straight +4 out, with no level control.
Not terribly useful.
So you'd be using up a stereo pair on your interface for monitoring (and since I'd be sticking to 8/10 channel summing for a while, this is kind of a dealbreaker for me).
Mind you, the unit I had on demo is for sale at a nice price, and it does sound pretty cool.

So yeah, now I've got to figure out where all this fits into my Gear Roadmap™.
And probably find a bunch of cash under a rock to buy the 8816.
Gah.