End of EVa and Rebirth are the OAVs of Eva series. They made them to clear some doubts Japanese audience expressed when watching the last episodes of the series. They're kinda optional, as the last two episodes themselves and I haven't watched Rebirth yet. To me, the real series ends with episode 24 and this is also for other EVA fans. The two movies are more or less a way to make some aspects of the original series clearer and to explain what happened towards the end of it. I know many previously EVA supporters that began to hate this series because of the last episodes and also because of the movies, which they described as unuseful and too complicated stuff to make you enjoy Evangelion. A real Eva fan should watch them, but if you're not a great fan of this series, you'll probably think Gainax turned the series into crappy and complicated stuff and you won't appreciate them so much. Anyway, you absolutely don't have to watch the movies if you haven't watched the whole show. Apart from the spoilers thing, you won't understand a thing of what is shown in the movies if you don't have a good knowledge of the series. They're not like CB movie or other famous series movies, completely indipendent from the main plot. If you don't know Eva, you absolutely can't start with these movies. It's for your own sake