My depth chart:
1) amoxicillin 2g 1h prior
2) clindamycin 600mg 1h prior (if I prescribe this it's usually because they're penicillin-allergic)
3) azithromycin 500mg 1h prior (I've only had to use this a couple times, both on penicillin-allergic patients with a history of colon problems)
The AHA guidelines are pretty specific, and doxycycline isn't anywhere in there.