the answer is- Yes you can improove.and a lot. but-
1)I would strongly recomend not to change xover unless you want to fine tune speakers a litle. you can change tweeter to 70000 series ring radiator you will get better dynamic ,more imediacy insound(just measure/calculate krell xover voltage divider or serial resistor to ensure the same eficienty with THE SAME voltage divider values)
bass drivers also can be changed to better ones (22W) bass will be fuller and more punchy not hard sounding .
what you can not change its midrange.yoiu can but its likely 99% that it will sound worse. even the same drivers with 1mm shorter coil will have diferent response and will kill krells enginiers sound conseption.
as for my self I am using aluminium enclosures also and they deserves very best drivers, better thant theese in krell Lat1 IMHO