There is no one audio component that makes a bigger difference in the sound of your audiophile system than your loudspeakers. Yes, there is the Linn (Scottish turntable manufacturer) argument that your system can only sound as good at its source components but considering the fact that you could have a fully decked out Linn LP 12 turntable with the latest modifications, upgrades and goodies running through wonderful electronics but into a tiny pair of audiophile bookshelf speakers and you would have a system that couldn't create any bass as if you had floorstanding speakers or a subwoofer.
Room acoustics are another key issue for any audiophile looking to make a better sounding room and the good news is that audiophile grade room acoustics don't have to cost a fortune or look terrible. The best tip we can give you is to treat your first order reflections with absorption. This is known as the area a few feet in front of your main speakers on the left and right walls as well as the ceiling. Many companies ranging from GIK Acoustics, ASC, Auralex and others make treatments that can match your décor and easily attach to the walls and ceilings. The next best trick is to deal with standing waves in the corners of your room's corners. There are products like RPG's modex plate and or ASC's tube traps that "eat these" standing waves and make the bass sound better. People claim its more taught, deeper and more in control.
Check out this list of the top audiophile speakers of all time at AudiophileReview.com. It's a great place to get a meaningful look at the best speakers ever made.
For other resources to help you with your speaker choices look to SpeakerHobby.com which is another good resource.