the MA BR2 is much more detailed than your warfedales 9.1
its a definite UPgrade (speaker wise)
however the problem i see is your amp
A marantz with MA BR2 !! - i hope you listen to "chamkila" music!
the highs will get irritating!
i would advice these speakers but not advice this combo unless you hear it and like it.
Also do not hear just one song- please try auditioning for an hour to notice if you feel fatigue
With the marantz amp i would look at PSB,KEF,Quad
if youve got a 20k budget i would look no further than the PSB B25 with this amp or a MS 906i or the KEF IQ10
if youve got 30k get the JAmo C405 : i would bet this woul go really well with that amp
BTW : whats the budget
Actually Magma - the PSB's for example are a far more brighter speaker brand than the Monitor Audio. Specific models have specific strengths but on a whole it is safer to say that the PSBs are more forward sounding, slightly more sensitive and also a bit more brighter than the average Monitor Audio speaker.
So, if the Marantz pairs well with a PSB, I dont think it would be too bad with a Monitor Audio. I have listened to the MA RS1 with a Marantz AV Receiver and regarding combination very very highly. That is a fantastic bookshelf speaker.
To the OP - I would not consider the jump from the Diamond 9.1 to the MA Bronze BR2 to be a significant upgrade. Instead I suggest that you plan for a slightly more substantial upgrade. The upgrade does not have to mean that you have to move from a bookshelf to a floorstander though. It could even be an excellent bookshelf - like the RS1 for example.