Recommend service to convert music CDs to high quality digital files

I use EAC. It's free software that will rip to most any digital format you want. Google it for more info.

If you have a PC equipped with a CD drive with which to burn CDs, I suggest giving dBpoweramp a try.  They have a 3 week free trial period.  If you like it it's only $39.  If you have a windows PC which doesn't have a CD writer, an external CD writer can be had for $30 or so.  I've been using dBpoweramp for years.  Rip all my CDs as uncompressed Flacs.

I ripped about 2000 discs with dbpoweramp. It is excellent, as suggested by @jazzman7 . Doing 50-100 discs shouldn't take very long. Unless they are classical and you want to touch up the metadata, you can easily do 20 in a couple of hours or less.

I would only have the CD's ripped if the resulting files were a noticeable improvement in the audio quality.

You won't improve on the original CD being played on a good transport, into a good R2R dac.

Cheers George