What I would do is to take a pad of paper with you, write down the make and
model of each speaker you audition and what you liked and disliked about the
speakers you were auditioning. Was the bass tight and deep or was it boomy and loose sounding? Were the mids life like or were they hollow or just too pronounced? Was the treble irritating and harsh or were they dark and not revealing or were they smooth that made you want to listen for more? How was the imaging?
Bring music with you that you are very familiar with and know quite well. To
make it easier to audition HT speaker systems, listen to the main speakers in 2
channel mode with music. Music is much harder to reproduce acurately then a movie soundtrack so if the speakers do well with music, then they will do well with HT. Speakers that do HT well may not do well with music. When auditioning the center channel of the same brand and series as the main speakers, , pick a difficult source like an announcer that mumbles alot. If you can makeout what the mumbling announcer has to say, then you have a good center channel.
I would go to speciality stores first and start auditioning speakers first
instead of going to the internet first. Once your likes are determined, you can
mention them here and fellow members can make internet brand recommnedations based on your likes/dislikes. The specality stores are better setup acousticaly then the big box stores which will make auditioning a little easier. It will give you an idea of what you like in a speaker.
Keep track of what amp or receiver is powering the speakers you're auditioning. Try to get a receiver/amp that closest resembles what you have or want to get. It just reduces another variable when audtioning speakers.
One thing to keep note off. When auditioning speakers, make sure the volume
levels are matched between the diiferent speaker pairs because the louder
speaker pair will always sound better. Listen to levels that you think you
would listen to most of the time because thats how you are going to be using
them most of the time. Blasting is fun too but only do it if you think you'll
listen to them at loud volume levels once in a while. Refer to my 2nd paragraph for a few points to listen too.
Now on with the recommendations...
My musical tastes range far and wide just like yours from classical to rock, blues to folk and everything else in between. I have picked my HT based around the towers to play music well. I went with PSB Image series speakers having the T45s towers, the older Image8C (now C40) center and 1B (now B15) surrounds. The Image series is a versatile speaker as it plays everything well with good imaging, broad deep soundstage, detailed highs without them sounding etchy or fatiquing, fleshed out mids and good tight bass.
There are a few PSB diehards in here. I'm probbaly their biggest fanboy on this site but what can I say. They work very well for me
http://www.psbspeakers.com/Image-home-theater-systems