Honorific__ ,
Via the assessment of the statistic between the business of your company and our company,we are in honour of informing you be evaluated as the "Diamond Class Client of XXXX 2008”
For assessment task of the clients,Our company via evaluating the statistic of the business between we and our clients,setting up nine classes together,they are descending as followed：
Diamond Class,Platina Class,7 Stars Class,6 Stars Class,5 Stars Class.4 Stars Class,3 Stars Class,2 Stars Class,and 1 Star Class.
级别这里翻译成Class 比Level更地道~以上是严格按照楼主的意思自己翻译的,