I agree on the upper mids on the Au24. Thus my interest in Tg Audio - with its killer bass and bass staging (a real weakness in the Au24), it is not as tipped up as the Au24, better stage... better with larger ensembles... BUT I would also recommend looking into Telwire as another option. But I love the TG Audio's stage and hall info myself... side note, the TG sent all my Cardas Golden Ref packing here.
Another thing, the power cables you use on your source and amp can keep the sound you love, and dial back the upper mid thing... I use isolation to get the stage I want, and power cables to help dial in their tone (with out jacking the stage up). So I would also look into maybe keeping the Au24 (for cost reasons) look into AC cords. Just give the Ac cords a couple of weeks to break in if new, and a few days if used, before really deciding one way or the other.
Another thing, the power cables you use on your source and amp can keep the sound you love, and dial back the upper mid thing... I use isolation to get the stage I want, and power cables to help dial in their tone (with out jacking the stage up). So I would also look into maybe keeping the Au24 (for cost reasons) look into AC cords. Just give the Ac cords a couple of weeks to break in if new, and a few days if used, before really deciding one way or the other.