I'd look at the aquatop heaters if you don't wanna bother with a controller. They have treated me well for a couple years so far on several tanks. They have a separate temp controller and probe that seems pretty accurate.
I got a used Apex Jr. just for temperature control (on a teco chiller and jager heater). They both have internal thermometers, but the extra bit of control just in case has been great. I ended up expanding the use like crazy with my Apex Jr. It now controls:
Chiller / Heater
Auto topoff (Neptune ATK), which includes a FMM module and PMUP
Fills my ATO reservoir using a solenoid, optical sensors, and another FMM module
Controls my feed cycles so I don't have to turn off a bunch of things
I use a VDM module to fine tune the speed of my return pump, and when I'm feeding it sits at 8% power to hold the water at a standstill instead of siphoning back
Neptune AFS for auto feeding when I'm away
Algae reactor light and fan (reverse photo period)
Sends me push notifications when levels are low or something is amiss