Somre are much better, others are not much better. To pull out my usual, tired band (yes, I do listen to other things!), there is a vast difference between the digital remastering of Metallica:Ride the Lightning ('84) on DCC Compact Classics/24 Carat Gold Disc (whoo!) and Metallica:Master of Puppets ('86) on the same label. Ride is pretty much the same as the original, but the remaster of Master is head and shoulders above the original. I think it may have to do with the original tapes and the quality thereof.
I can't speak to the remastered Rush albums, but I have read an article that says that the Rush albums have been moving towards worse and worse mastering as time goes on, so the remasters of the old ones could be quite good, or they could have been ruined.
Try going to a shop with used CDs to find the old ones. I've only had to return used CDs a couple of times; the rest of them have worked really well.
Ken
