hi again all

Now that I am pretty happy with my amp I am just wondering about a couple of tweaks.
Can anyone tell me if I change R1 to a 1megohm (R2 is removed) if I will expect an increase in signal -and what impact would this have on gain?

What impact does changing the values of c3 or c4 have - can this help further tighten up the bottom end?

thx

Ryan