Don’t know the AHB4 – did you mean AHB2? Regardless, just get a switch and adapter cables and run your phones off the Benchmark amp. [See Benchmark AHB2 - the power amplifier for your headphone (and a guide/walkthrough)] Or, stay in the iFi line and get the Pro iCAN Sig.
Safest bet is within product lines you already know you like. If you feel like dabbling outside of that, try to get to a CanJam.