That's about what my enclosures run for temps when I'm not heating the whole room, which I generally have between 75* at night and 78* during the day.
I'd say that it is beyond worth it to spring for a high quality thermostat. I run Herpstats exclusively in my room, a few of the H2 Redline and one Herpstat 4 currently. They're certainly not inexpensive, but they give me peace of mind which is priceless.
I also drill holes directly through the vents to make probe placement simple and versatile when needed. I know it's hard to drill holes all over those cages though after waiting 25yrs for them.
Sounds like you're close to dialed in though.