In my case, I would put in
Base stats: 1620
Crit chance: 42.5
Crit damage: 50
To compare my crossbow I would then take its stats as they show on its weapon tooltip - 1010.9dps, 0dex, 0%cdam:
The second crossbow would be input as 902.6dps, 102dex, 124%cdam (including socketed gem):
My tool tells me this will change my DPS by about 7520dps, which after the 15% quiver attack speed increase becomes 8648dps. The in-game damage is displayed as 24653.58dps vs 33517.34dps = +8863.76dps. This is close enough (since I have +min/max dmg stats on my amulet).