I think this is where dealers can truly earn their money. As many above I too believe speakers are, overall, the most defining component of a system, but a chain is only as strong as its weakest link so you need to make sure they're driven by upstream components that mate well with them.
This is where a good dealer comes in. They should(emphasize should, if they are truly a good and knowledgeable dealership) know what amps/preamps/source/cables work well with certain speakers and should be able to demo these synergistic combinations. If a dealer is using the same components to drive various speakers, beware you may not be hearing the best out of a given speaker(some dealers will do this on purpose to push the brands they want to sell). For best results you should call the dealer ahead and let them know what you want to hear and what your system goals are, and they should warm up the appropriate equipment(very important) and have it set up for your audition when you get there(obviously you'll bring your best demo music with you, along with the music you listen to most frequently).
Assuming you are able to do this, the next crucial step is auditioning your final contenders at home, preferably with the compatible upstream electronics if you're going to be upgrading those as well, either now or in the near future(again, a good dealer will be critical here). Admittedly this is an arduous task, but it is the only way you'll be sure you're choosing the best equipment for your tastes that you know will work in your home. For the amount of money you'll probably spend and the amount of long-term enjoyment a well-chosen system can provide, it's well worth the effort. Best of luck.
Tim
