I must ask if you have tried the speakers with a different amp? If the tweeters are bad, or not working, it can sound like a blanket is covering the speaker. Also, can you verify that the MA5100 is operating properly, especially Bass, Treble controls, and HF, LF, and Loudness switches.
As far as speaker recommendation, read my post here and click on the links provided in the post,
I think the speaker would match well with the MA5100, and IMHO, absolutely perfect for the music you listed.