That's right, Amazon has Power Ranger Samurai in 5.1 Surround Sound. Good timing as it seems Netflix is having issues with their HD licensing right now. It is also available for free for Amazon Prime users.

Update: Power Rangers Zeo through RPM are now posted on Amazon as well now (Power Rangers in Space is labelled Power Rangers RPM). No sign of MMPR yet. Also, you can purchase the movies as well.