The Pioneers should sound very similar, I've only noticed the Fluoroscan ones to sound very different from the rest. I personally think $450 is too much. However, tuners will always be, in many cases, more expensive than amplifiers because they are more rare. I am assuming and I could be wrong when CD came into play tuners were forgotten and probably thrown away to save space for the "better" items.
But, the SA-7800 is really a nice amp.
I was wondering if anyone has heard the Pioneer SA-7800, and TX-7800. I am just wondering how they compare to my SX-950. The SA less power, but that doesn't mean everything. There is a guy selling those on CL. It is probably about a 45 minute drive from my place. He is also asking what I feel is a bit much. $250 for the amp, and $200 for the tuner. The tuner seems more overpriced than the amp. Still, I was wondering how they would compare. I would likely not keep both the SX and SA, if that helps. I am not going to buy it just for fun, I don't need another rig, and I don't have tons of extra space.