As with any other pre/pro, the difference is largely going to be one of priorities: the pre/pro (especially when produced by a smaller company with less expansive R&D resources) sacrifices some bells and whistles like network connectivity while placing greater emphasis on performance (things like the DAC's that Peter mentioned).


Price-wise, it's not clear yet, but I suspect the Model 978 is closer to being a successor to the Model 990. The balanced outputs certainly fit that notion, at least. It sounds like the Model 998 will be almost a peer to the Model 978 except for Trinnov - although I wouldn't be surprised if they decided tuck in another tweak or two on the Model 998 before it was all said and done.


In theory, Trinnov's 3D remapping has the potential to really distance it from Audyssey, but getting it right appears to be tricky (to put it mildly) so we haven't yet seen a really definitive implementation of it in a consumer-level product. Audyssey has dominated for years now, though, and one reason for that dominance is simple: it's a pretty effective tool for what it is. There are also a number of different degrees of sophistication to Audyssey that have to be factored in, as well. At it's most basic, Audyssey is a quite good automatic setup tool with a pretty decent room correction aspect. As you step up the levels, the room correction gets more sophisticated and can do more to help compensate for undesirable room conditions.


I liked my Model 990, and I like the sounds of what has been described for the Model 978. I think their goal is to match (or exceed) the Model 990's sound quality in conjunction with the new features. From a model number perspective, I could see someone describing the Model 978 as a "Model 993" - following along the same lineage as the Model 990, but with Audyssey as a more expedient alternative to the Model 998's Trinnov.