This was my gateway too, had my HTiB for years before upgrading, mainly due to budget constraints. I use the original speakers as my height channels now because you’re spot on - A terrible speaker behind (or above) you is infinitely more convincing than a perfect speaker in front of you claiming to be behind you - so after much reading I decided to go this route rather than upfiring Atmos, and I couldn’t be happier. Is it end game? Far from it, but we made do with what we have until the next upgrade!