I have Bowser’s Challenger, but not the Big Boy.
The popularity of Big Boy models as been increased with the 4014 tours. But beware of buying one on Ebay. Many of the early Rivarossi/AHM lodels are being offered at high prices. Those early models all have the old three pole motor in the cab and very deep whel flanges that will not run on code 83 rail. Parts are also an issue. Rivarossi sold out to Hornby and parts are not available for many of the old locos.