Can anyone with an 861 v6 give a view as to how much the v6 opens up the top end and detail or is the limitaton the DSP's??
Soundstage size is pretty much identical between the v4 and v6, but the v6 is a much (much, much much

) more accurate processor. Instruments, voices and other sounds are more defined, withing the soundstage. There are details that simply were not there on the v4. Now that I have the v6, I can say there's no way I could live with a v4 anymore.
Also you shouldn't compare a DSP setup from Meridian to a analogue setup with a Class�. If you're interested in analogue speakers, use them on a 861 with analogue output cards.
If you prefer analogue speakers over DSPs is up to you. There are some excellent analogue speakers out there, both passive and active. In my opinion, the Class� isn't anywhere close to a v6 with analogue output cards, but if you're interested in one do a side by side demo and see or rather hear for yourself.