Modular design is a nice idea in the hopes of future-proofing, but not knowing what needs to fit in those modules makes it a nearly impossible task.
A much better approach would be a reasonably priced pre-amp. Onkyo receivers can stuff nearly all of the latest features into a $600 receiver, which has amplifiers as well. The only problem with the budget receivers is that you may not be able to drive your speakers if you have a mid to large sized room, or if your speakers are harder to drive that the average speaker. If Onkyo released a pre-amp for around $600 to $800 with all of the latest features (the very best version of audyssey, the very best video scaling, 11.2 preouts with audyssey dsx, networking, etc.) as well as balanced outputs, then people wouldn't mind upgrading their preamp, when some new cool feature comes out that they just have to have. However, in the current state of things, the most economical way of getting all of the latest features (the ability of doing height and width channels simultaneously, the very best audyssey, etc.) is to spend nearly $2000 on an receiver. If I spend $2000 on a receiver, I am sure as heck not going to upgrade it every couple of years. I had better get 10 to 15 years out of the thing.