Rcprince, you're very close. When converting Linn systems to Aktiv, you install powered crossovers in the amps, thereby the amp only has to generate power for the bandwidth each driver will produce. You then completely bypass the crossover in the speakers so each channel of amplification goes directly from the amp to the driver.
Yes, it is a significant step up from passive configuration (i even went Aktiv with the surrounds in my HT), but I agree with you you'd be in a huge compatability problem using other speakers. You'd need something with the same crossover points to start with, and then you'd certainly be voiding any warranty you have on them.....in short, I wouldn't recomend doing it.