Totally agree with Helix here, I have heard some Fyne's recently (Think they were the floorstander 501) and they are are just too shouty in the treble for me so I suspect the 500's would be similar, system matching will be a must with these, but they are very detailed and lively performers, the bottom port works brilliantly.
The Focal 906's is a very nice loudspeaker, not only in build quality but in sound quality, when I owned them I found them very balanced and really enjoyed them, detailed but still smooth with a very nice midrange (that inverted alloy tweeter is a gem) and they get my recommendation, but they do require a few hundred hours to get the bass working properly. However I sold them in the end as they seemed to have a strange response in the bass that kept niggling me, bass extension was reasonable and better than the specs suggest.
Considering the OP is very happy with his Concepts, and only requires to fill in the low frequency, I think his answer would in this case be a compact ported subwoofer tuned below 60Hz, I am generally not a fan of subs with music but in this case I think it would work for him especially if he is not planning on disco levels of volume (to annoy his neighbours) most subs do have volume controls you know so he could just turn it down a little.
BTW maybe forget the Wharfedale 12.2, I tried the 12.1's a few weeks ago and they were not as good as expected (crap actually) which goes to show you should ALWAYS listen for yourself.
Lastly, I am currently using the Elac DBR REF62's and unless you have a very beefy amp forget it, they suck power like you wouldn't believe, but I'm still loving them.