I strongly suggest that you IGNORE the previous passive characteristics. Let the DEQX do what it does best. A lot of passive crossovers are designed with computer models , then tested and refined in an anechoic chamber and then further fine tuned in a given R&D room. This is to say- It ain't YOUR place.
In contrast, a DEQX has a mic input and full RTA functionality as it relates to YOUR personal listening room. Your room acoustics are taken into account when the DEQX puts the crossover together. That's a HUGE advantage. In addition to that- the DEQX qualifies each driver. What specs may be found for a given driver are done in proprietary labs with proprietary equipment boasting exaggerated results. The DEQX will see the driver for what it really is and make the appropriate compensations (if need be). Then when it's all said and done- the DEQX can put the EQ curve you prefer most on the final result. Most loudspeakers are designed with an end result in mind in terms of linearity. If you prefer a flat response from your speakers- you can get that. Rolled off highs? Inflated mids? Why settle for one? Most recordings benefit from some level of EQ on the playback end. It's all there for you to explore in the parametric EQ presets that can be flipped through on the fly from the remote.
To answer your first question- is 55 watts enough?
In a word "Yes".
remember that you should put some caps on the terminals to avoid any junk from your amp getting to the fragile HF drivers. Just because you are filtering the freq before the amp- the amp may be spitting out small amounts of low freq hum that is NOT being divided by the DEQX. It only takes a little to blow a tweeter. With a cap on the terminals for protection- you will be running them in a pseudo-passive/active configuration. So 55 watts active isn't entirely correct. OTOH, most db output ratings given for a driver are measured at the standard 1 watt/1 meter. A few watts is enough to run you out of the room if it's clean and fully active. 55 watts in your given scenario is enough to blow the cones/diaphragms out of the frame. Be carefull, and BEST of luck. Great piece of gear!