NAD takes on the Krell Beast 1800 vs 6700??

My friend has a Adcom 700 CDP,Krell KBL linestage,NAD S-200 amp 225wpc.Diva 6.1 speakers 88ohmHis friend is selling a Krell KSA-250 250+ wpcWe listened to the Krell for one day then the next day the NAD.The Krell was run balanced with a Transparent Audio Super Link power cord.The NAD was run unbalanced with the stock power cord.The Krell had tactile kick drum slam,clear highs and very clean mids.The soundstage was wide but lacked depth.I was surprised at the flat soundstage.Imaging was so,so.Overall it sounded boring.With the NAD the very first thing I noticed is how it almost sounded 'tube like'.It was smoother and warmer.The soundstage was not quite as wide as the Krell but it had real depth.Imaging way better.The NAD won hands down.WHY??