firstly, i had a set of alpine type E's and i will never have them again! they were sh**e IMO. spend the extra cash on the type R's mate. as has been said, its better to spend more initailly and be happy than to go the cheap route an want to replace them straight away!crossovers - filter the audio signal so that the mid driver gets the mid range frequencys and the tweeter gets the high range freq's.as for fitting, anyone can fit car audio, and i mean ANYONE. it really is not worth the cash they'll charge to have them installed somewhere!just take your time when removing door cards etc so as not to break anything and you'll be fine. if i were you id spend the extra 50 quid on getting better speakers and fit them yaself, instead of paying someone 50 quid to fit them!