I have a Kobo mini and I disrecommend it--I don't know if the bigger version is any better for PDFs or if they do PDFs at all, but as far as I can tell, if you use Calibre tags, there's no way to get Kobo to use the tags. I find it really frustrating.

I hope someone has a good suggestion for you; my PDF-reading solution is a Kindle DX but I don't think that meets your other criteria anyway.

Edit: There are a lot of things I like about my mini! Just, for you I think it is not the right one.