I've got a pair of Alesis Monitor II's in my B room... I'll accpet condolances later

Mostly used for Jazz - 20%, Rock -60%, Metal - 20% of the time.
The sound is not great, no highs, no mids... just a big boomy 10" woofer
the Mid is a 5 1/2" with a 4" dome tweeter.
Big dips in the sound at 250hz, 1k and 5k. (crossover points???)
Totally rolls off at 18khz and not very responisve above 16khz...
I'm wondering if these things could benefit from new Peerles (Nomex?),
VIFA (Kevlar?) or Hi-Vi drivers?
Would the crossovers need to be re-done as well?
Or can the cross-overs be shot to begin with hence the bad response?
Worthwhile investment, or just get rid of them???
Thanks for any help and recomendations.