Audiophile Classical cds?

Looking to broaden my classical collection. I don't really know much other than I have tended to enjoy what gets termed 'warhorses' (Beethoven and Mahler's 9th, holst - the planets) and also the more serious chamber pieces.

Need some recommendations to get things rolling. Top notch sound is a must have as I have found that it really keeps me engaged. I'd like to get a set of 15 or so must have classical audiophile cds. Any Ideas?

Cheers, Nik