[Kosh75287]

Is it worth it to me to have an extra 100fps when my Underwood 185grain gold dots are 1200fps?

I'm not sure, but one of the questions preceding that one might be, "CAN I have an extra 100 f/s when my 185 gr. Gold Dots are 1200 f/s?"
At 1200 f/s with a 185gr. projectile, it sounds like you may be at the max end of the velocity scale, until pressures rise into the .460 Rowland range.

I'D CHEERFULLY trade 185gr. @ 1200 f/s for 200 gr. @ 1100 f/s or a bit more. Hodgdon reports 1142 f/s with their 8.2/CFE-Pistol/200gr. LSWC, but it's from a test barrel, and "real gun" velocities seem to dip under 1100 f/s. IF, with a .45 Super "upgrade" (sans "fully supported/ramped barrel"), I could get 1100 - 1150 f/s without stretching or battering anything (much), I'd be inclined to try the "upgrade".