I'd definitely put in ethernet. But maybe there's some way you can wire everything through 1" PVC pipes, so it's relatively easy to replace it.
For Wireless music you can also using Apple's Airport Express?
I don't know how expensive solar panels are where you live, but here they are definitely worth it, especially as they get subsidized by the government. Another good green thing is a big tank which uses all your overheat to keep water warm, and then uses it. Don't know what it's called, but it saves quite a bit on the heating bill.
Solar thermal and solar hot water preheat is usually a big win. It takes a lot of energy to heat water. Heat in the form of natural gas is still dirt cheap, but you'd be saving a lot of carbon footprint.
Thermomax tubes can collect solar energy to heat water, even when it's freezing outside. You can also use their output as part of a radiant heating system.
You also might price out getting photovoltaic, and writing your own controller so that a small auxiliary air conditioner (separate from main system) gets turned on, but only when your panels are producing enough juice to run it. This means you are getting all the benefit of "free" cooling, without paying for a battery system and without paying for enough solar panels to run the AC for a whole house, and getting this boost exactly when you need it. (When the sun is beating down on your house.)
You can also look into air heat exchangers. This lets you preheat your ventilation input air with heat from your ventilation output. This only works well for super-sealed super-insulated houses. (The Germans even have a standard for super-green houses that includes such devices.)
In Houston, the air quality varies with the tides. If you are in a similar situation, I'd look into a custom controller that ventilates the house when the air quality is good, but seals it when it's bad.
The conduit is a good idea. If not everywhere, then from various strategic locations, maybe running up and down to basement or attic.
It's an auspicious week to advocate this because Apple and Intel just released Thunderbolt, formerly known as Light Peak. The initial implementation is all copper, but the protocol is designed for fiberoptic, so within five years we may all be routinely plugging keyboards and monitors in one part of the house into a computer in another part, which in turn is plugged into the storage array in the attic. But only if we pull the cables.
+1 for PVC pipe in the walls. A friend of mine did that, and it's worked on great for him.
If you have vent system for heating and cooling, it might be worthwhile to look at smart systems with per room control. In my house it's all or nothing, so the bathroom can be 85F while the living room is 65F. (My low tech solution was to cut out thin cardboard from cereal boxes and place it under the vent covers. It's visually unobtrusive, easy to do, and makes a big difference in the heating / cooling effectiveness.)
For Wireless music you can also using Apple's Airport Express?
I don't know how expensive solar panels are where you live, but here they are definitely worth it, especially as they get subsidized by the government. Another good green thing is a big tank which uses all your overheat to keep water warm, and then uses it. Don't know what it's called, but it saves quite a bit on the heating bill.