what amp under a grand?

I have vienna acoustic mozart grand marantz sr5005 avr,marantz 8001 sacd,vieanna theatro center,b&w 600s3 for rears,current amp adcom 555mk2.looked at used parasound hca 2003 thx, rotel rb 993, and and an adcom 5802.im fine with the performance the marantz gives me for ht but for two channel sound is muddy. i think its the amp? any advice on a used amp that would bring out the detail of the mozarts?