You've already had the suggestion of one metal cleaner BRASSO, I suggest another, over here in the UK it's called SOLVO AUTOSIL. It's a chrome/aluminium polish which I use for getting scratches out of perspex.

Have you tried copying your CDs on a PC with a CD writer? You could always edit individual tracks as WAV files if you needed to. At least you could make yourself working copies so that you could 'rest' the originals and it might be a good idea to make copies before you try and clean any rare CDs.

Scratches on a CD are more likely to affect the tracking than the reproduction especially if they occur in the TOC (Table of Contents).