while it's true that sources are extremely important - gi=go, my sources are about where i want them now. (except tunas - at least i have about 50 i can play with!

) digital and analog playback are set. as is preamp. the preamp is a key player, imo, as everything interfaces with it. get the best (tube) preamp you can afford (with low output impedance) and build your system from there.
then, play w/speakers. there's so many different types, as have awreddy been mentioned - 2-ways, full-range multi-ways, line arrays, horns, planars, full-range single-driver, omni's, etc. try different flavors to see what works best for
you. speaker-room and speaker-amp synergy is also critical. i am presently set in the amp department, as i have amps that will work well w/most any speaker i care to try - high power tubes, low power single-ended tubes, medium-power single-ended tubes, gainclones, and even a coupla s/s offerings, for my subwoofer set-up. (i could use them for main speakers as well, but i much prefer tubes - even for speakers that require power - tubes on top, and s/s for actively crossed subs is the best of both worlds, imo.) as far as room goes, my present ~18x40 listening room is ok, but it's a studio apartment, so it is shared with everything else. in a couple years, i hope to be back in a situation where i can have a ~26x38 listening room; then my present infatuation w/horns should really be able to be appreciated - i presently am able to sit ~9' away; but i know that a min of 12' is what's really needed to make these babies sing properly.
ymmv,
doug s.