It depends on the active crossover. It also depends on what slopes and type filters you want to play with... it'll cost you bit more in long run too. You need two amps or more(depending what you want..2/3/4/5+ way,ect.), bunch of cables/wiring,ect. If i was actively crossover anything though i personally wouldn't use tubes personally. i wouldn't mix tubes and solid state either. Phase respone and impulse response can get little weird... There is more studying i think then spending on wanting to go active route. If done right you can get double the power and increase driver phase and sensitively compared to a passive filter. Cause no matter what passive filters saps up and dissipates unused power from the amp and cause loss in sensitively and damping factor. Thats why sometimes they suggest using an amp twice the output than the input of your speakers. Active can improve lot of things but it's time, space, and money.. It can be lot of crap.