I'd try the Stage One first. It's made to go together really. The B&K is not so special sounding of a pre/pro that you really need to rush out and absolutely have one, in my experience...but then I've sold lots of pieces in the past on a retail level. I used to sell both B&K and Aragon lines(actually, the previous Aragon line with 200x5 and Soundstage however). I did use and sell the B&K ref 50 however. Again, It doesn't shame any of the better pre pro's that I could remember sonically...if that's what mattrers to you.(sound qualiy is everything to me in a pre/pro...all else, distant 3rd). Don't get me wrong, it's descent enough gear. But it's not better than the competing Classe, Krell Showcase, Anthem AVM20, Primare, even outlaw 950(yes, the outlaw is cleaner and less colored!) or likely the Aragon piece!
I guess what I'm saying is, if you're after the Aragon amp in the end, I'd go with the Aragon match, because it likely works together.
good luck either way.
If you went B&K, I'd probably stay B&K