Well, first of all, if you're planning an internet radio station, (don't know if you are or not), TM Century and some of the other "radio library" suppliers may not be of much help. Some of their contracts with the record labels prohibit selling the libraries to any other than "professional" radio stations. Perhaps that has changed in the last year or so, but the last time I checked, you pretty much had to be an over-the-air station, with all ASCAP, BMI and SESAC licensing in place.
Also, you need to be careful. Even some TM Century libraries (and others) have the "wrong" versions of oldies. I have found a few remakes and re-issues in them. And, I'm just not a fan of the "no noise" CD's anymore, from a position of pure sonic quality.
The Time Life Series are, generally speaking, pretty good in terms of being original hits by the original stars.
But, to get what you need from CD will generally cost you a couple thousand dollars, before you have a substantial enough library.