I have used Linn active systems for a while and can tell you that the difference between pasive and active is very dramatic. My first experience was using a Linn AV-5140,
3 way speaker, using one amp. Then I got 3 amps (Klouts)
and used them in a pasive triamp way, the little gain did
not justified the expense. Then came the active cards for the amps. The speakers crossover where removed and the difference was huge. My next experience came when I got a
pair of Totem Mani-2, to this date the best speaker that I have owned, the sound was incredible in the pasive configuration but they where hard on the amps (85 db at one meter), I when an got two way cards for the amps (Klouts), the improvement was even more impresive that with the AV-5140. The next experience came with a pair of
Linn Keltiks, these are active only speakers, I use four Klouts to drive them. Linn have always included the option
to go active with their speakers and amps, they have the
"Tune Box" that allows to use the active boards ( two, three or three way with isobarik bass) with non-Linn amps.
Krell, Naim and Meridian have such systems. I have seen ads
on stereophile for active crossovers, I believe that the manufacturer is Pass Labs, so you have quite some options.
Linn's tune box uses fixed crossover points, I am not sure on Krell and Naim. The one that I belive is made by Pass Labs is adjustable. This is one of the best upgrades you can do to a system, too bad so little manufacturers take advantage of this. My best advise is to tell you to go to a Linn or Naim dealer and ask for a demo between pasive and active systems, your best bet will be a Linn dealer, the speakers can be changed from pasive to active by changing a plate at the back of the speaker. Hearing an the
same system pasive and active will let you evaluate the improvement and evaluate without spending a penny if the improvement will justify the cost. Hope this will help.