What are the Sutta stating Paramithä requirements to be a stream winner? I have heard, therefore I am yet to discover in Tipitaka, that to achieve certain stream winner stages, one needs to fulfill paramithä. Could you please give me the names of some sutta which I can read further on this (or the Tipitaka vagga / section). 

Ten Paramithä
 1. Däna
 2. Sîla
 3. Nekkhamma 
 4. Pañña 
 5. Viriya 
 6. Khanthi 
 6. Sacca 
 8. Adhitthana 
 9. Mettha 
10. Upekka

Thanks in advance!
Could you please give me the names of some sutta which I can read further on this

I think that SN 55.2 implies perfection of Sila.

People say that Dana parami is an essential beginning, for example here ...


  Giving (dana) is one of the essential preliminary steps of Buddhist practice.


... but I don't know a sutta where it's named as a characteristic of a stream winner.

I wonder where the talk about practicing paramithä came from. Have you encountered people or books that speak of requiring paramithä to become a stream winner?

There are a couple of talks on Access to Insight.


The Ten Perfections
A Treatise on the Paramis


I didn't find any (after only a brief search) on dharmafarer.org

My theory is that "perfection" isn't a doctrine which is talked about in the suttas.

The "Ten Perfections" for example starts by saying,


  Each path was defined as consisting of perfections (paramī) of character, but there was a question as to what those perfections were and how the paths differed from one another.


So I guess those doctrines (the doctrines about "perfections") were developed after the suttas.

The "Treatise" talks about the sequence in which they should be developed, and how to practice them and so on:


  Here "sequence" means sequence of teaching. This sequence is rooted in the order in which the paaramiis are initially undertaken, which in turn is rooted in the order in which they are investigated.


It finishes with:


  Their fruit is, in brief, the state of perfect Buddhahood.


The introduction says,


  The "requisites of enlightenment" are the paaramiis themselves, the main topic of the treatise. The word paaramii derives from parama, "supreme," and thus suggests the eminence of the qualities which must be fulfilled by a bodhisattva in the long course of his spiritual development.




So far as I know, when Theravada talks about the Four stages of enlightenment (starting with "stream winner") it's more usual to talk about the "fetters" which are overcome, rather than about "perfections".