The Syteks are in a different league from the Presonus pres. Put it this way, Justin Timberlake's vocal on the Black Eyed Peas' record - Where is The Love - was put through a Sytek MPX-4Aii. Can you picture them having considred the Digimax LT as a contender? I can't!
If you buy a Sytek you can opt to have Burr Browns on channels 3&4. This gives a slightly different character for these channels when compared to channels 1&2. Kinda like giving the unit a split personality.
If you opt for Burr Browns on 3&4, you can also buy the conversion kit ($80 approx), which includes another two Burr Browns and your 2 stock ICs that were originally intended for channels 3&4. This enables you to convert channels 3&4 back to stock ICs. Or, alternatively convert channels 1&2 to Burr Brown. All options open.
Here's some info
on Mike Stoica who makes the Syteks.