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Comparison of pure power amplifiers (AA3PRO, AA2PRO — require external preamp/DAC with volume control; shortest signal path, highest purity, most upgradable) vs integrated amplifiers (A12PRO, A11PRO, A12 PURE — built-in preamp and often DAC; most convenient, one-box solution). Signal path comparison: power amp = DAC→XLR→amp→speakers (2 stages) vs integrated = DAC→preamp→power section→speakers (3 stages). Upgrade path: power amp stays through preamp/DAC upgrades; integrated requires full replacement. A12 PURE as hybrid: integrated now, one-key switch to pure power amp mode when upgrading preamp later.