Simple power amplifier with feedback - designing procedure
From the base of T1 to the output, this is basically an inverting amplifier with a feedback resistor R1. So I can simplify this circuit to this:



simulate this circuit &ndash; Schematic created using CircuitLab
The amplifier &quot;amp&quot; contains all the transistors and what you need for biasing them. (Note that your amplifier doesn't have a real + input like my &quot;amp&quot; has. But that's OK, your amplifier responds to voltages relative to ground. My &quot;amp&quot; does that too as I connected its + input to ground).
Now it is easy, you want a voltage gain of
\$\frac {V_{out}}{V_{in}}= \frac {18}{1} = 18\$.
This is an inverting amplifier with feedback configuration (read more here) so the voltage gain is simply
\$A = \frac {R_1}{R_2}\$
So \$ R_2 = \frac {R_1}{18}\$ = 8.9 kohm
Note how the value of \$R_2\$ will not disturb the DC (biasing) that you so carefully calculated. There's a capacitor in series with \$R_2\$ so for the DC biasing nothing changes!