just curious if hearthfire has anything that adds to dawnguard, or more, dawnguard adds to hearthfire.

Very unlikely.

As a rule, DLC (For any game for that matter) never adds content to another DLC. That way, you aren't required to buy both to obtain all the content from one as it were.

I noticed one of those coffins from Castle Volkihar are available as an upgrade for your cellar. Was pretty happy with that, but that's all I noticed. But it's also entirely possible you can get that without Dawguard.

More and more it's looking like I'm leaving work early to go play this game. I wonder if that coffin gives you the bonuses that the Dawnguard vampire coffins give you.

You get a coffin in the cellar if you're a vampire.

I got a rescue mission from Gunnar an hour before H was released "Rescue Hod" Now I have to rescue him from vampires to get some logs!!!

He better not die.

I just made a coffin and yes, you get the "surge of vampiric power."

On a side note, holy crap you need alot of iron to make a furnished house.