What a coincidence! Just last week I was at some fancy audio/visual store in manhattan (on 58th street between lex and 3rd ave -- though I can't remember the name of the place for the life of me). They had a number of stunningly beautiful demo rooms, including one room that featured the flagship speakers from Wilson Audio(an MSRP of about $135,000) and another featuring a bizarre speaker from B&W called the Notilus. They seemed to specialize in a very select few speaker companies, Wilson, B&W and another company called Linn. I was fortunate enough to be given a quick demo of many of the different speaker lines in these companies and one of them was the B&W 600 series, I was especially interested in these because they were about in the same price class as my epic 60/500 series. The 600's are a beautifully designed speaker, and in the 5 minute demo they gave me of them, they performed very nicely -- a very warm soothing signature, but it doesn't hurt that the rooms were acoustically treated and the speakers were being powered with, by the looks of it, some extremely high end seperates. I don't imagine you could go wrong either way between the 600's or the m60's.
If I may quickly pay a compliment to the M60's, I spent that day listening to some of the best equipment in the industry, in rooms treated by experts, and with interconnects that cost more than my whole system(ONE of the speaker wires connected to the Wilson Alexandria cost $4500!!) and when I got home, my m60's sounded not even slightly worse than it did the day before. Don't get me wrong, my system cant hold a candle to those sonically, and the M60's are just a tad bright for my taste, but they perform much better than the price difference would indicate, and I don't imagine the 600's specifically would be an upgrade over them(WAF maybe, not sonically though). From there, the choice is yours.
