Why noise when increasing amplification of last cascade of transistor amplifier?
Q1 does not clip, but Q2 does clip from insifficient base bias current and Vc rides too close to the 3V rail.

There are a lot of interactions with changing bias resistors.


Q2 has RC1 as the source impedance 1k1
The input Rbe diode AC impedance lowers with rising base current from 2.6uA to 24uA (Rb=680k to 300k, Rcb= 100k) and drops from 8k to 1.1k thus attenuating the Q2 base voltage 15% to 50%  
raises Ic = 1.6mA =100(3-0.6V)/150k to lower   Vc=1.6mA*1k1= 1.8Vdc from 3 to 1.2V to prevent clipping
Reducing Rb alone  however causes more positive base current thus lower Rbe thus more negative swing gain and THD  
overall Neg feedback V gain is ~ 22 as shown  with no impedance gain 1k1 in:out