Ramadan: Prophets after Muhammad (pbuh)?

[Rumaitha - OneUmmah!]

Why is there a need for prophets after Muhammad (pbuh) if he had been sent with the last scripture/book and the perfect religion?

If Ahmadis answer this question, please answer this as well: You accept all six Sahih books that the Sunnis use, but deny all those that contradict/conflict with the Quran according to the translations you use. But, for all those you reject, they do not contradict the Quran with the translations we use (Hilali/Khan, etc).

For an example, the phrase (???? ???????) Khaatam Annabiyyeen - The seal of the prophets, has many different opinions on what it translates to. The majority of translators agree on two translations: The seal of the prophets, the last/final prophet. So, why is seal then translated to "mark" or "greatest" instead of final/last? Hadiths from the Sahih books clarify that Muhammad (pbuh) was the last and final messenger and prophet, and that does not conflict/contradict the verses of the Quran, but your translations of it. So, why then, adopt new terms or translations for the word Khaatam, instead of using those Hadiths discarded in which prophet Muhammad is stated to be the last and final prophet and messenger?