I use the vintage Pioneer SF-850 in my main reference system. This is just me but I don't particularly care for the sound of opamps. I prefer the sound of a traditional gain stage (transistors or tubes). This particular Pioneer is reasonably transparent. I rebuilt the power supply with some new diodes, Elna Cerifine caps and Jupiter beeswax as bypasses. The other active crossover I use is the Audio Research EC-3. It's fully tubed with 12 - 12AX7's. Bill at Response is playing with it right now. It is a nice crossover too but way overpriced in todays market.
The Pioneer is very flexible. As you can see from the pic, you have easily switchable XO frequencies and easily adjustable slopes. To my knowledge, no other XO (current or vintage) offers this kind of flexibility while providing a traditional gain stage (read=no opamps). IMHO, this is an absolute must
, especially went you start crossing speaker over into the upper bass range and above. The AR EC-3 is a nice XO. You can easily adjust the XO frequencies but the slopes are fixed at 12db. That often works but at times isn't enough in other situations.
There is a Pioneer SF-850 on eBay right now. It should sell for less than $1k. The AR EC-3's, though far more limited, can sell for 50+% more than that. Fortunately, I bought mine years ago when they cost far less.current eBay auction
The SF-500 and 750 don't sound near as good as the 850.
While I haven't fully explored the Marchand's it appears that they have a fixed slope, which might work in your situation. Also, it appears that you change the XO points by swapping out boards but with this solution, you need to buy extra boards.
The DEQX's out there seem to be enjoyed by some. With these you have almost infinite adjustability. Trouble is with these, they take your analog signal, convert it to the digital domain where you apply XO points-slopes-EQing-gain adjustments, then you convert that processed signal back to analog and pump it out to your amps. For some this is a good solution, for me, I'll stick with my all analog approach.
Though I haven't listened to every active XO out there, I've owned and listened to quite a few. For my needs, the SF-850 has been the best and most flexible solution for every set of actively crossed speakers I've set up. YMMV