I personally think your not going to hear a significant difference
That's my guess. A friend said that though my Pass XA25 was less power on paper, he didn't think the Belles would be significantly different enough. It's also 20 years old. It's not a lot of money, but I think I am over the initial fever toward "snapping it up" and will just consider the $$ saved as going, perhaps, to an amp that might really mix up my options.
Also, good point about the different op-amps @mapman . I think the hypex I've tried has a fairly good one in it -- see, this review -- but I think it likely is just too bright for my taste or space (or both).