The XP has WAY more functionality than a 2.0s. I've owned the 2.0s, the 2.2X, and the 2.2XP. The XP has processors so fast that ALL corrections are done instantaneously.
You don't have to use a laptop, but with the XP connected to the laptop you can play with XO frequencies, slopes, target curves, and even the unprecedented dynamic room correction, which is basically a variable loudness control.
Boz told me recently they're working on a crosstalk elimination function that will keep signals from the left speaker from going into the right ear.
This also shows something cool about the XP - it's still under software development where I doubt the others are. As they release new functions, they become available by easy download. It's not future-proof, but it is still current and a kick-ass piece of gear.
I don't have any experience with mods to the units, but I've heard nothing but good. One thing - I don't like the stock DAC sound. Maybe it's primarily the power supply or the DACs need better parts, but overall I have enjoyed outboard DACs out of the digital outs much more than the stockers.