Amphilophus xiloaensis or Amphilophus sagittae would be your best bets from the "Amphilophus" family for smaller versions as they ussually stay between 8"-10", Have yet to hear of them larger then that. tangledupincichlids.com has some in stock.
What are the other cichlids in the 125? Amphilophus xiloaensis (the fish in my avatar are xilo's) are believed to remain smaller than midas. My 2.5 year old male (the white male in my avatar) is approx. 11" TL They also, ime, are not quite as aggressive as citrinellum so long as they are given adequate space. My big male has been in my 125 his entire life and has coexisted without issue with several other cichlids of all different sizes. He is easily the boss of the tank and occasionally gives chase to flex his muscle but he's never caused any physical harm to another fish.
Oh and check out the midas in this tank from the Shedd Aquarium in Chicago. No way would these guys work in anything smaller than a 75 gallon and the biggest males in this tank would look extremely cramped in a 75.