Most of the blogs I have encountered suggest to use Nginx with PHP-FPM. I have seen benchmarking results, and they all seem to be impressive, when compared to Apache with mod_php enabled. But fact worth noting about my case is that we serve 3RPS at peak time. Changing Apache with Nginx is not an easy process. Maybe somebody could give any advice, if it is worth migrating servers in our case?
Probably not. You did not mention if 3 rps is for dynamic requests only or all requests. Even if you meant dynamic requests, I do not think the migration is worth your efforts.
I suggest the following migration path for you: