Best Classical to "broaden" listening arena?

I have come to "love" Yanni, Norah Jones, Sade, Sarah Brightman, etc.

Since I really appreciate individual instruments & have a fairly high end system with separation as a strong point--I am interested in which composer / group I should start my "classical" specific collection with?

On Audiogon, Classical seems to be the highest sold category thereby indicating high collectibility & listening by educated music lovers.

Thx in advance for your opinions,

Dr David Joned
If you have a public library near you, most let you check out classical music cd's and see what you are drawn to.
Go to Amazon or other music sites and sample their music. The sites also will suggest similar works and what other people liked as well. It is free and you will get to hear 30 second clips to wet your whistle. (check out Frederick Fennell conducts Leroy Anderson @Amazon)!

Compilation/Sampler CDs from Chesky, Telarc, Reference Recordings etc, are also an easy way to get excellent quality at a fair price. HD tracks lets you hear first as well.
I assume you are looking for more specific recommendations, and especially some that are well recorded, spacious, and engaging. For violin, try some of Hillary Hahn's Sony recordings, such as Mozart, Barber & Meyer, Brahms & Stravinsky, Mendelsohn, and Elgar. For cello and piano, try Zuill Bailey's Telarc recording of Brahms works for cello and piano. All are quite accessible.
If you have streaming capability check out WFMT Chicago. Best classical station in the US. Special shows St. Paul Sunday and Exploring Music will raise your knowledge and focus your interest. Other great show besides daily programming
Check out:
I believe St. Cecilia was the patron saint of music. This is a site dedicated to classical music. Not religious in any way, I think the title is from "Hail Bright Cecilia" by Handel or Purcell or some such.