speaker criteria
1. If your married then I'd say the Wife Acceptance Factor is your most important criteria.
2. the more sensitive the speaker is the less powerful amp you need. Class D amplifiers generate more power with less heat.
3. do you have room enough to keep the speakers set back from the wall? Some speakers require that they be set back from the rear wall. If you have to place the speakers up against the rear wall, I'd recommend you look at the Harbeth brand or the KLH model5.
4. take a look at this video for a general overview.