My question is about bi or triamping.

Why are so many of the active crossovers I'm finding set up with 1/4 inch plugs for PA or sound reinforcement? I want to build a triamped system around dynaco tube amps for mids and highs and Adcom for bottom. Any reasonable priced active crossovers available that are flexible enough to work with quality drivers I install in self built cabinets? I loved the last system I had that was biamped using home made speakers and want to go triamped with this system.

I have a Marchand XM-9 Deluxe and am very pleased with it and active systems. The quality of the parts is fantastic, although they aren't much to look at. They offer 2,3 and 4 way, both fixed and adjustable, in both tube and ss. Sean is quite right about the ability (and perhaps desire) to use whatever you want if you assemble it yourself, wire, connectors, upgraded power supplies (My next project) etc, or you can have one built for you. Building one is very simple, it takes about 8-12 hours (I'm slow, I know). They come with RCA or XLR inputs and outputs, so you won't have to deal with the 1/4 to RCA adaptors, which you have to use with some of the equipment you have found. I had a Furman crossover prior, just to try out active crossovers and was sold on the idea. The Furman, although pretty good (I upgraded the OP-amps) leaves much to be desired, compared to my XM-9.
Have you thought of a nice 2 way crossover and a sub crossover? This may improve your options and keep the adcom only running the non-directional stuff. I would much rather hear the tubes for the whole vocal range and just let the adcom do what it does best-be a workhorse.

By the way, many older dynacos actually limit the highs and stress the mids (which they do really well). When I had my MKIVs redone, the guru actually eliminated something to improve the highs. I wish I remembered what, resistor, cap? It did help. His theory was that 30-40 years ago, the only thing that went above 15khz was "hiss". None of the recordings nor most of the speakers really produced the upper ranges so many designs added circuits to limit the hiss.