Amorous Adventures SE and Amorous Adventures Extended SE blew my socks off.

[Celedhring]

Those two mods are seriously GREAT.  I did the main storyline with Serana along with Sexlab Amorous Adventures and Amorous Adventures Extended.   The Serana storyline doesn't stop with Harkon getting destroyed at the end of the Dawnguard but actually extends into the Temple of Dibella. And best of all, the Sisterhood of Dibellia storyline dovetails into it perfectly as my PC was going to be a Dibellian priestess. 

I haven't finished the Sisterhood of Dibella storyline yet, but I finished Serana's storyline throughout it all..definitely makes her a favorite companion of mine due to her backstory. 

Mind blown.  If only there was a similar mod involving Zora Fairchild...