I seriously doubt a second barrel would be needed for a mere subsidiary dial. That arrangement is most often used on multiple complication watches, or simply to extend the power-reserve.
And if THAT impresses you, I'll see your two-barrel movement and raise you the Vacheron Constantin Patrimony
Tour d' ile, ref. 89000/000R-9655 Limited to just 7 pieces, it was manufactured from 1990 - 2000 (MSRP: $1,500,000.oo)
The movement contained
FOUR (2-doubled) barrels powering a tourbillon, perpetual calendar, and eleven other complications for a potential total of 270 hours of running time (11.25 days), but capped off at 250 hours.