best preamp for a MC-252 for under $1500

Your best bet would be to spend the money on speakers. Running your cd player through your amp shouldn't be a problem. Do some reading and ask for help. Forget about distortion specs on amps and preamps as most are so low as to be a non issue. The Mac amp you have is a very good amp and some Vandersteen, Theils, Rocket, PSB and numerous other brands will sound better than the 901's. Different speakers sound different even though one may be as good as the other. Your ears will have to decide. There's a number of small companies that have speakers that are great for the money at audiocircle.com. Ask questions as people love to help. Bottom line is your speakers should be the most important component to replace imo.

It could be your power. New power lines usually only cost 2 to 400. Only you'll be able to tell if it's the power. You may consider getting a power conditioner like a Powervar or Oneac for the cd player and see if that helps. The power supply in the Mcintosh is no doubt excellent and may be why you're not hearing the problem with that amplifer.
When it comes to speakers you'll find alot of different tastes. Many companies these days make great speakers for the money. There's a few at audiocircle.com that are standouts as well as other companies that sell direct so they have no advertising or middle man markups. You'll have to find the reviews on these stars yourself. Ask here as well as audiocircle and audioasylum and then do some research. Most importantly take your time.

First let me qualify this by stating I've been a dealer for 2 mos but have owned VMPS speakers for 9+ years and have been recommending them as a must listen for years. Rather than take my word for it here's a list of current reviews:
http://www.audiocircle.com/circles/viewtopic.php?t=13112
Also the RM 40 won Best of High End at CES 2002 and runner up in 2003. These will handle all the power you have from the RM2 on up and sound excellent doing so.