You can see a recent discussion about this, as well as a link to the info on an Onkyo unit that is configured in a modular fashion Here .

The sword of technology cuts both ways, unfortunately. In the case of an upgradeable unit, it would seem that those of us loathe to blow our 401k's on a new pre/pro would want the security of an upgradeable platform.

However, the manufacturer would have to be very careful in how it implements its upgrades so as to ensure compatibility and ease of installation/usage (and still offer a warranty). The result would be upgrades that are slow to arrive and expensive. Not to mention the fact that the consumer would rely on the manufacturer to continue support of the old hardware once a newer standard comes along (as in the PC world, but even less likely).

My guess is, unless Onkyo's unit makes a business case for configurability, we'll continue to recycle our hardware (or keep it and show people proudly that "they don't make 'em like this anymore" ).