I have a Allen & Heath that is for all purposes just the shell of it original self, having been completey redesigned with a new master section, summing amps, grounding...
ITB does not hold a candle to outboard mixes from my standpoint and I even use some outboard gear inserted in the some AD-8000 channels I reserve for that purpose and don't feel like I am suffereing in great loss in almost any case with that extra DA-AD cconversion. I putting a BA6A on a snare sometimes is just what you need and there is nothing that I can do ITB to do that. I automate my volumes and some plugs in PT and do some manual automation on my console for Aux riding and sub-mix fader rides and I am cool with that and get some killer results. We just got our first shiny record so things can't be that bad!!!
I will say that a board that doesn't sound good isn't going to help matters. Some mid level boards that you are describing might not sound good and owing the the mostly 5532 based designs in that category you can have mixed results. You have to learn what each of these boards are really doing to your audio when you are pumping a hot mix through them. Some boards in the mid-level do not regulate power to each channel and when you are slamming signal to all the channels, there is some debate as to distortion arising as a result of the power suck from the main supply rails. As far as I'm concerned, there is no debate there. Also, none of them clip nicely, or have the robustness in sound that the discrete counterparts can have - I learned this first hand with the overhaul of my board which was completed in steps - so I have been able to hear the change in the sound of the board in stages. But again, even without clipping individual channels you may feel like your mix is caving the board in. In these cases, it is better to leave yourself some headroom, not push the board to hard and I think you can wind up with a clean potent sound.
As an aside, Thomas, the master section on your Saber can be made much better and the noise floor can be dropped quite a bit. Of all the mods that were done, the master section made the most improvement (so did raising the SN ratio 30db in a worst case scenario!!!). Look at the schematics - poor grounding layout and they even ground the audio to the chassis on every single card in the board.....big no no. PM me if you are interested.
-josh