$1500 is a steal, but if I had relatively efficient speakers (more than 87 dB/w) than I would still get the Rotel. I have compared the two and the Rotel seems to have a little more air and a deeper soundstage than the Sunfire. But you should compare the two yourself before making the decision.
I totally agree with David. $1500 for a $4000 amp, wow, I must say that is one heck of a deal. If I came across a deal like that I would jump on it without hesitation. I own a Sunfire CG Sig II and I absolutely love it. Of course the final decision is yours (although a deal like this one doesn't come around every day ).