Yeah, i know about the crappy Samsung service. I contacted them myself today and i was getting pretty flimsy feedback but she said that they are working on it.
Like i said, its the Samsung software that is gimping on AMD systems for reason unknown. I explained this to the "Samsung tech chick" and the confirmed and replied that Samsung is working on that so only time will tell.
In your case there is actually something you can do about it because i was getting the same low IOPS as you until i found something.
If you follow this guide, your SSD will work much faster: Sean's Windows 8 Install & Optimization Guide for SSDs & HDDs