You're going to need some specifics here -- sound systems go up into the hundreds of thousands of dollars.
My advice is to get a good receiver and speakers of the consumer level, and call it a day. That's about $700 when you're all done. The option I would look for is the ability to have more than one set of speakers, or to do 5-speaker surround, so you can add speakers wherever you are lacking.
For example, my primary unit is really good with highs and lows, but needs midrange. At some point, I'll stir my lazy ass and get some midrange speakers for full sound. It's not as important to buy a matched set as to pick speakers that sound good in the ranges you're seeking. Most audio stores and even some Best Buys will let you bring in a sample CD. I use a CD-R that's mostly "Onward to Golgotha"