When looking to buy CD copies of early albums it is always best to look for the original recordings. The reason for this is the Loudness war, most modern CD's are mastered to be louder, this might sound like a good thing, but louder is better when you turn your volume up, if the recording has been made louder then it doesn't really make it louder it just means that every thing is at a constant volume of the listeners choosing, rather than constantly varying in volume like music should naturally. Some remasters from the early 90's are very good, such as the remasters of Queen albums from around that time, also Remasters by MFSL, are always masterd with sound quality in mind. Not all remasters have been mixed that loud, while others have been mixed so loud they sound distorted!

If you want to hear the music how it was intended to be herd then look for older versions of the CD's and stay away from newer remasters.