I think it matters, but how much, I don't know.
The idea behind the PAC is very good. It seperates the digital noisy domain from the analog domain. Digital circuitry is barely impacted by noise, but in the analog world (like your ears) noise is an undesired "sound".
I don't know if Yamaha designed the PAC out of necessity (the noise floor of the analog outputs of the Montage was unacceptably high (maybe because of higher clock speeds of the new SWP70 tone generator?)), out of financial needs to bring down costs (the PAC board is designed once and can then be used on all kinds of high-end instruments) or out of their desire to continuously improve their instruments.
The Tyros 5 is already very quiet noise wise, so I doubt you will hear a difference. Maybe with a headphone?
The perceived sound quality has more to do with the choice of the samples, the sample time length, things like SA2 and DSPs than with PAC, I believe.
Hopefully Paul (pjd) will chime in. He has much more knowledge than me in this area. On his site sandsoftwaresound.net
he writes about the PAC:
Pure Analog Circuit is probably the least understood and least appreciated feature of the Montage. It’s not just better DACs, people. The high speed digital world is very noisy as far as analog audio is concerned. Yamaha separated the analog and digital worlds by putting the DACs and analog electronics on their own printed circuit board away from noisy digital circuits. Yamaha then applied old school engineering to the post-DAC analog circuitry, paying careful attention to old school concerns like board layout for noise minimization and clean power with separate voltage regulation for analog audio. Yamaha’s mid- to high-end products have always been quiet — PAC is pristine.
Since the PAC board is a separate, reusable entity, I could see Yamaha adopting the same board for GENOS.
Some other articles by Paul describing the PAC:
Another advantage of the PAC is balanced audio out, which means even less noise picked up by the cables going to the mixer/monitors/PA system.
Hope this helps,