electret Mic preamp, how to improve design?

[Deactivated-1]

I made this mic preamp for an electret mic, but it suffers from a bit of bias excursion when I bump the mic, I'm new to solid state electronics so how would I fix this? maybe by adding a resistor in series with the input coupling capacitor? so like a grid stopper - base stopper? 
other than that it sounds pretty good, just a little lacking in mid frequencies but I'm guessing that's just the cheap electret mic I used, should order those panasonic ones everyone's talking about...

oh and testing the circuit in LTSpice it's not perfectly balanced on the outputs, I know that... I had the design of the circuit a bit different and decided to change it after I already made the circuit board... yes ik, very smart 
so now with the changes the outputs arent balanced, but I didnt care about that much since I'm just using it as a desk mic and dont care that much about some noise.. my room is noisier than any mic will be anyway 

so anyway, should I just add like a 10k resistor in series with the base? will that reduce the gain too? (without considering the voltage divider formed by the ..base leak resistor and the one I'll be putting in series)

I attached the schematic of the circuit, and pictures if you're interested how it looks

[bob91343]

What is bias excursion?