That depends who you want to tell it to. If you are talking to someone who knows pinyin, then use É. There is no need to confuse things by reinventing pinyin! But - if it is for someone who does not want to know or learn pinyin, then Eh is not good - as that is more of an 'A' sound. I think that maybe 'err' would be close. Or I think that it is also like the ur sound in Curve or Bird. Is that close enough? (edit) - Err in British english - http://howjsay.com/pronunciation-of-err or even http://howjsay.com/pronunciation-of-er

"a" when it is a classifier, the sound is like 鹅 but we need to rise tone。

Generally speaking, in English we do not spell out the sound of letters from the alphabet. The letter "E" is pronounced "E". 一 has the same sound in English, since English does not use tones.

now I see what's the most distinct difference between me and native English speaker--I can't even understand what you are trying to ask... Oh my..how can you guys understand the asker'a question. I need learn harder.lol