Both versions call for BC109. BC109 comes in 3 HFE grades: A, B & C. Ungraded parts could be any HFE, but are probably in the bottom 2 tiers. Any high-gain, low-noise NPN such as MPSA18, 2N5088/5089, BC549C would all be good subs. Mind the pinout if you sub parts. The older version has a charge pump that doubles the rail voltage for more headroom. When you say "doesn't do much" I assume you mean doesn't make distortion. If you want this to play dirty, then ditching the charge pump might get you there.