it would all depend on your budget really as the options could be endless.
the size of the speakers are a fairly common size and changing them for a replacement will be an easy task, as most stereo shops could do it in no time and probably keep them in stock.

in my old Escos i had Focal Utopia's, quite pricey for what they are, but just like other speakers they fitted directly into the standard positions and holes with no cutting or nasty alterations to what was on show - it all looked factory.

your best bet will be to nip into a decent local car stereo specialist, they should be happy to help, after all your going in with a nice car and wanting to put money in there pockets