I'm replacing my 80v2 with them. You might want to try the M5s in front to compare them with the LFRs. I'd be curious to know the soundstage size and imaging differences between those two. The v4 came out in June 2014, consisting of albino, aluminum dustcaps and a new tweeter. Since then however there have likely been more refinements to The Family of Curves and hence at least the cross-over. If your 800 has white dust caps and a phase knob, it's v4. I've had my 800 now for almost a year and I still can't say enough about it.

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated