Mark Noble supplied this photograph of his IMF TLS80 and a description (below) of his perceived differences between the IMF TLS80s and Naim SBLs which he also owns.
I think the SBLs work pretty well, being very revealing, accurate and providing a wide dispersion (you can sit well off-centre and still get a decent sound stage). The boxes are small and very dead to the rap-with-knuckles test. Their weaknesses include a general over-brightness and, in my room, a suck-out in the mid bass, although low bass comes through fine and is in no way woolly. Also you have to wind the volume up to get them working properly, otherwise the sound is rather thin.
The IMFs couldn't be more different. Fairly obviously a more 'traditional' sound - if you're my age. At first they came across as bass heavy and a bit dull, but after a couple of days, as my hearing adjusted, this went away and their strengths come through. Probably the change is due to listening at lower volumes. It is unnecessary to use these loud. The physical size of the boxes must help here. I'm sure there's more air on the move at lower volumes. Anyway, for their age, the IMFs are really good. Ultimately less detailed than the SBLs and the bass is not as well defined - sort of more 'rounded'. An obvious difference is the lower stiffness of the cabinet, even though IMF reckoned the TLSs were strongly braced, I guess age and the box size are against them. This does show up in the sound sometimes.
Type of music - well, the Naims are better overall with recently recorded rock/pop but the IMFs work wonders with classical/orchestral/organ where the power in the bass really comes across and on older rock recordings where the less detailed approach helps for the wrong reasons!
Which is best? Overall, the SBLs. But it's nice to have a choice and I won't be selling the TLS80s. Wouldn't half like to hear the RSPMvi !!
Incidentally, the creasing that I was on about on one of the B139s turned out to be exactly that. These units, as you will know, in some versions, have a thinnish paper/plastic film covering the face of the panel. It is this that got a bit of a crease in it when it was glued to the actual panel. As predicted, no effect on the sound - the quality is identical to the other (uncreased) speaker.
Finally, as you might have experienced, Naim use those two pin plugs on their speaker cables. To use normal loudspeakers, just undo the screw that holds the plug together and treat the plugs prongs as (4mm) banana plugs, which will fit most speaker screw terminals. Not perfect, but low-hassle and a reversible technique.