about cap missile speed... its a lot about perception. - fighter missiles "look" faster cause you are much closer to them when you fire them, and they have a trail that suggests speed.
capital ship missiles are indeed faster.. - but when one fires them ( well, except for the BHG gunship ) - the distance to the ship is much greater. and they have a smoketrail that does not suggest high speed. ( like the rheinland engines that look like they are just puffing out little clouds of smoke instead of thrusting the gases out - or the funny impulse rings on the liberty ships... they never look like they go "fast" )
if capital ship missiles had the same trails as for example CDs, they d look much faster of course. a little cosmetic change can make everyone "feel" the speed of a missile much more than actually increasing the speed.
allthough i am a great supporter of improving missiles... i think 250 on battleship missiles could be a bit too much. - but thats just a feeling, something like that would have to be tested extensivly.