When purchasing music from a website for the first time, try just one item first to confirm compatibility with your car audio system.

Download 2.0 Channel Stereo files (no higher than 96khz/24bit) in AIFF, WAV or FLAC for maximum compatibility with your car audio system.

HD Tracks

HIGH DEFINITION MUSIC
The World's Greatest-Sounding Music Downloads
(most songs are available with album purchase only)

How to rip your music CDs to FLAC

MP3s are convenient, but no matter how high the bit rate, they're still lossy music files. We'll show you how to rip your music CDs to FLAC files, which are superior in sound quality.

iTrax

The tracks on this site are the real deal...no, CD quality is NOT high-resolution as others might have you believe.
(many songs available for individual download)

Exact Audio Copy

Exact Audio Copy recognizes inserted audio-CDs automatically – once you chose one of the formats and the tracks you actually intend to copy, the ripping-process is ready to start.

Bowers & Wilkins Society of Sound

Subscribe to Society of Sound to download high-quality albums from Peter Gabriel’s Real World Studios and the London Symphony Orchestra. All available in Apple Lossless and studio-quality FLAC.

MAX

Max leverages open source components and the resources of Mac OS X to provide extremely high-quality output.
melodishop.com is another site that I'm checking out. I'll let you know how it goes. You deposit money into your account. It looks like the minimum deposit is $30. The per song prices seem very low, compared with other sites. (Not sure I'm going to recommend this site, but if you check it out, let me know what your experience is.)