Welcome, Peter. First, although this may be only a matter of semantics, depth and warmth in sound are characteristics of the original recording; we should be looking for speakers which accurately reproduce those characteristics, neither increasing nor decreasing them with unusual dispersion characteristics or response fluctuations. The M22s do this at a relative bargain price, but you may be disappointed if that's not what you're looking for. In my view, they're ideal.
The M3, M40 and M50 use a different driver for the mid-range than do the M2, M22, M60 and M80. That area is slightly depressed or "laid-back", which some prefer and which tends to make some poorly recorded pop items less intolerable.
