I am impressed by Presonus' approach to features, user interface and integration. They seem to be better at thinking about their products from the perspective of a real human using them than most other audio product makers.
That said, I was not particularly impressed with the sound of the two Presonus products I've used.
The first was a row of preamps in a 1U box, don't remember the model number. The sound was thin. Seemed like the top end was rolled off (gently, but noticeably), the noise was higher than I would have liked, and the analog output levels were positively anemic. Even with headset mics we had to add more gain at the line-level input on the console.
The second was a StudioLive 16:4:2 mixer. Again, the output levels were really low. Even with the output trim cranked, devices downstream from it always needed extra gain. I suspect that was probably a cost control measure as beefy output stages are expensive and most users probably aren't interfacing with downstream devices the way I did so probably wouldn't ever notice or care.
Note that our experience with the preamp units was about five years ago and the mixer about three years ago, so it's possible that things have changed. I'd just recommend listening before buying and making sure you have the option of returning whatever you buy if it doesn't play nice with the rest of your system.
As for the Focusrite stuff, maybe test with your system before committing to owning one. The comments here seem to be divided between people who love 'em and those who just can't get them to work. Apparently some users have had issues with drivers.
You might also want to add MOTU to your evaluation list. I haven't used their stuff (yet), but they appear to offer good value and I haven't noticed anyone complaining about them (although that COULD just mean no one is using them!
).