I am new to the site and to the idea of a reader however once I was presented with the idea of a reader I fell in love with it and want one ...NOW.

But I am also not the type to waste money on something that is not a good "fit" for me.
I have considered the Kindle (1 and 2), Sony 505, and also have been looking into the iphone (mainly due to the Kindle app). I have searched Amazon and love the selection they have.
However I need an important question answered (sorry if it sounds like Im 5...I am just new to all this)..I need to know if I can read books that I get from places other than Amazon ( I know sony is out but curious about things like fictionwise, booksonboard, public library, etc).
I like the fact that Sony 505 supports Epub and some of the things I have researched lead me to think that more books might become avaliable in this format and I hate to think I might miss out on a particular series of books or such because I have a reader that does not support it.
I have only considered the iphone because I am due to get a new phone in the next two weeks and I was thinking it would be great if I could "kill two birds with one stone". I know the reading experience on the iphone will not compare to a stand-alone reader however I think it might be a good intro into the ebook world. I know I will be able to read the kindle/amazon books on it, however I also understand that there is another reader on it as well...can anyone tell me about this if it even exists?
Ok one final bit, below are my
desires/concerns can anyone tell me which (if any) of the above would be a good fit?
**large selection of avaliable books (both free and purchaseable)
**Expandable memory (not sure now much I need and the K2 nor iphone expand but then again I dont know how much it takes to store a hundred or so books)
**Like the dictionary function (but not necessary)
**PDF reading is not high on the list of needs - Reader will be used for reading e-books only
**Not crazy about having someone else (amazon) backing up my library but I do like the fact that if my husband gets a kindle as well, we both can access the other one's books.
**no need for wi-fi (I am ok with downloading/moving books from the computer)
Sorry it is such a long question session but I figured the more info, the better answers I will get

Thanks in advance, this site is awesome!