BPA is based on the same output transistor as the NO 33H. Power is higher on the AMP2 at 150x2 vs the BPA2 being 125x2. The BPA is the better sounding amp.
Is your judgement of the sound superiority of the BPA based on A/B comparison with the AMP2 or the output transistor? I have a couple of AMP2s and an AMP3 and have wondered from time to time about buying one of the newer higher power Proceed amps. OTOH, the AMP2 sounds clean and transparent to me and has more than enough power to drive my KEF 104/2s, so I've also wondered if I'd just be burning more energy.
I have had the Amp 2, Amp 3, HPA 2, HPA 3, and the ML 433. All are very good amps and I could easily live with any of them, I use less efficient speakers than you do so I kept the HPA's and ML 433, but you shouldn't need that much power so if you're happy with the Amp 2/3's, keep them.
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