Crossovers are indeed complicated. It's hard to out do an Engineer/Designer as an experimenter. It's hit or miss. If you miss, you could end up with blown drivers fairly easy. A lot are hard to get. Especially tweeters that blow easily. If there is a proven upgrade, then you have a better chance. After experimenting with speakers years ago, the best I found was to leave it to the pros.
Possibly change to better grade caps in the passive crossovers (same value) in there now would be an option.
As far as keeping it all analog, I don't know if that could be done with something like the Behringer you mentioned. It has a time delay in it, and that most likely does it in digital. Could it be bypassed? Also, all the op amps, capacitors, and who knows how much other active electronics added to the mix, that could add something else sonically.
The pros have the high dollar test equipment to work with, and see the after results too.
Possibly change to better grade caps in the passive crossovers (same value) in there now would be an option.
As far as keeping it all analog, I don't know if that could be done with something like the Behringer you mentioned. It has a time delay in it, and that most likely does it in digital. Could it be bypassed? Also, all the op amps, capacitors, and who knows how much other active electronics added to the mix, that could add something else sonically.
The pros have the high dollar test equipment to work with, and see the after results too.