Diff recon: change ratio aswell?

[Vronsky]

Dear all,
Garage diagnosed worn rear differential.
Found a shop that specializes in diff reconditioning.
Am wondering if I should have the ratio changed now that diff is taken apart anyway.
Current ratio is 3.42
Car pulls reasonably well, but does make quite some noise at 3500-4000 rpm.
If I lower the ratio (3,27), I expect the engine will become quieter, but also less powerfull.
Increasing the ratio (3.64) will give more power, but also more noise, I assume.

Your comments/recommendations are highly appreciated.