Keep in mind you are seeing a delayed reaction on your gauge when the thermostat opens. The temperature it reads is the elevated temperature at the sending unit (exit point) just before the coolant from the radiator reaches it (reading the heated block coolant first). There will be a temperature rise from the coolant in the block before the coolant from the radiator reaches the sending unit after the thermostat opens.

A 190° thermostat could easily read 210° at the sending unit prior to the coolant from the radiator reaching it, then settling down to normal temps which could still be 10-30° higher at the exit point of the motor than at the radiators exit (entrance to motor).

High flow thermostat;
180°
http://www.summitracing.com/parts/mil-16401/overview/
http://www.summitracing.com/parts/mrg-4364/overview/

160°
http://www.summitracing.com/parts/mil-16400/overview/
http://www.summitracing.com/parts/mrg-4363/overview/