The OP is asking if higher end monos "could" be a significant sonic upgrade.
IMO absolutely yes is the only answer, but the real question is how much is the OP prepared to spend, because price is MORE OFTEN THAN NOT an indication of ultimate quality.
Example: the difference in sonic quality and price between the Deltas and the new 7 series from Soulution is vast.
One way to be sure of the pairing is to ask Wilson which amps they use when they display/demo at Munich and/or Axpona. They'd know better than anyone here how to get synergy with their speakers.