Ivan,
I have never seen the afterburner but did have email conversations with Eric about this device. With that said, it is my understanding the simple explanation of the afterburner was, it was an add on device that increased the power into the coil by using higher voltage batteries. I believe the voltage was over 20v at maybe 22V or 24V.
There are a couple of ways to increase depth and one of those ways is using something like an afterburner. Another technique would be to reduce internal noise. There is another method that has merit but requires attacking the reasons for the noise itself. Part of that noise comes from the damping resistor and another part comes from any input resistor into the preamp. Reduce the noise and then the gain can be increased.
Both techniques can be addressed but not without additional expense. So, lets see what might be done in the future.
BTW, it is my opinion both ways to increase depth can be done with an add on device if necessary.
Reg