GM transmissions aren't known for their quality at stock HP numbers. There are some things you can do to lengthen trans life with average bolt on mods. Ultimate heat is what blows transmissions. More HP allows the engine and transmission to spool up faster which generates more heat. The gears themselves can take a bit more than stock HP but it won't last long if you're running 1/4 miles all day. Adding a trans cooler can go a long way, but it merely prolongs the inevitable. Upgrading to stronger internals is the most viable solution. You're on the right track though, it's best to upgrade the driveline first before sinking cash into eking out more HP.
My GT is stock, I have a drop in Amsoil air filter but nothing that adds hp. I run full synthetic engine oil which frees up HP that would have otherwise been lost due to friction.
If you do plan to upgrade your transmission, look into getting a shorter final drive as that can be the equivalent to adding on 20-30hp with excellent response, although if you drive a lot of highway you'll lose some mpg due to the higher sustained highway rpm.
'11 Ram SXT 4x4 quad cab - 5.7L V8; 128,200kms
'09 Malibu 2Lt 3.6L - 140,000kms purchased 1 March 2019
'06 Pontiac G6 GT - 3.5L V6; 162,000kms (rear ended 15 Feb 2019, and given totalled title by insurance)