2003 Galant, yes way off topic.
And I have no idea. With some time though you can improve what you have now and surprise yourself how it compares with other cars.
Changing thermostats is easy. You'll need:
Rubber O-ring for thermostat
The thermostat housing is circled in red. Bleeder screw is in the middle of the housing.
Remove two 10mm bolts from housing.
Pull off housing - you will lose coolant don't worry, refill later. The thermostat sits inside.
Scrape off old gasket material on both surfaces BEFORE remvoing the t-stat.
Remove t-stat, install new one with new o-ring.
Put gasket in place, bolt everything back up.