I'm thinking: What exactly is it that you feel is missing, or must change
with the sound of your system?
Or is this just a case of upgrade-itis ?
Coz... replacing a pair of Merlins... is not easy to do!!!
A BAM would improve them. But create more bass issues in the making.
One could get a Behringer unit and use it's dsp and room correction facilities to really work
wonders... you place it between the drive and the dac and rock on!!!
A skilled dsp-artist... (I guess you would be that then - pushing the buttons and all..) can really change the sonics of a system with
this type of unit. That is a viable option here, I should think!
You could add them Holograph tri-forks or whatever, behind the speakers.
I know that you got something called Svano miljoteknik helmholz resonators - bass absorbers in the US now
those are superb at notching out bass problems, it all comes down to ... I feel - I might be off here by a mile but I'd rather just say it:
You know the Merlin's - Make them work!

Waddabout' it?
Imperial