I don't have personal experience with YPAO, but I can tell you that no combination of an SPL meter, test tone series, and hours of manual tweaking can beat the accuracy and almost ridiculous ease of the MCACC. Adding an external EQ to your system may be easy. But you really need a real-time spectrum analyzer to properly adjust it. What's great about MCACC/YPAO is the fact that it packages all these elements right into your receiver almost transparently.