The choice is too system dependant. Any component could be the weakest link. Cables can be the difference between good sound and "magic", so they are important too.
I say buy the best speakers you can and work from there. Amp and pre-amp choices will synergized with the speakers. Source components improve most any amp/speaker combo. Use cabling to fine tune your system. Change the speakers and you may need to start all over except for source gear.
I say buy the best speakers you can and work from there. Amp and pre-amp choices will synergized with the speakers. Source components improve most any amp/speaker combo. Use cabling to fine tune your system. Change the speakers and you may need to start all over except for source gear.