None's required, but many "lesser" products than Meridian processors have HDMI switches already. Some of them are on replaceable modules, which is almost for sure going to be cheaper to upgrade than buying an HD621 or whatever comes after it.

As HDMI switches go, the HD621 is pretty pricey (though yes of course it does more than just select 1 of N HDMI signals), not that Meridian's customers are likely to be that sensitive to that. There's an argument that keeping all the digital video electronics out of the audio processor might be a good idea, however, at least if there's any analog stuff.

G68XXV, Oppo BDP-103, ATV, Sat/DVR, Sony PJ