Where shall I go in Cambodia and Vietnam?

I'm probably only going to have 2 weeks to fit in as much as I can - can someone suggest a route to take and what not to miss? I'm thinking a couple of days in Phnom Penh and Ho Chi Minh each and take in killing fields, angkor wat, cardamom mountains; mekong, markets, halong bay etc. Can it be done in 2 weeks?