I've had good luck with AJ Michaels. Used them multiple times and even a couple times they fixed the issue when I thought I would need something replaced and only charged the service visit.

A lot of the big guys really push replacement and expensive parts without trying smaller things first.

Third on Saddleback. Had it for years and it has been great.

This person has the right idea but I would really recommend getting a 4" filter and putting it on the back. This will allow for more air flow which is important for removing dust.

If you want to kick it up a level I use a Corsi-Rosenthal box in my house. Modified design with 3 two inch Merv 13 filters. Merv 13 will filter out viruses and pet dander.

Here is the design https://engineering.ucdavis.edu/news/science-action-how-build-corsi-rosenthal-box and you can find a lot of Youtube videos on how to build them and some testing them https://youtu.be/lbWiZSsEqPg.

I recommend getting a decent fan instead of a cheap one as it should be able to pull more air through the filters.