Yeah, Seakeeper got back to me this morning and said the 450 is rated well for the R-25, and "if there was room, the 525 would provide even greater performance."
Since I know
@JMarshallR25 has already been living with it on the exact boat and the price difference is significant, I'd probably just go for the 450 myself if I get around to it.
Was your discount something special or just something you found online? I'd be aiming to do the install myself most likely.
I'll also be curious to see how your underwater lights and wire routing get handled once it's installed.