If you're feeling like having a lot of fun, I'd reccomend linking to area51 (KDE for FreeBSD's development repository)
http://freebsd.kde.org/access.php
The version of K3B in there is the 1.70 beta-1 version. From what I've read about it, there is no DVD support (some conflicting dependency issue) but CDs are working more or less alright. It's probably your best bet as it uses all kde4 libraries and HAL and DBUS and crap like that.
I haven't tried installing k3b on a KDE4 box yet so I can't really be much help in that regard, but I imagine it can't be done easily. A lot of the new stuff in KDE4 really gummed up the way K3B expected to do things
. Not that the changes weren't for the better, it's just rebuilding k3b has been a big job, and the original developer hasn't had the time.
I imagine by the time 4.4 is in ports (this has been delayed due to them wanting 7.3 out before they commit massive changes like X.Org 7.5 and KDE 4.4. Qt is at 4.6.1 and more than ready for the transistion.) they'll bump the k3b-kde4 port (only in area51 currently) to 1.90, the first release candidate which has 100% of it's features working (reportedly in Linux)
It's been a bit slow since AFAIK the kde-freebsd and k3b projects are both hurting for developers, and the 7.3 release cycle makes committers a bit wary. Break the tree for a major release and people will burn effigies of you in the streets :O. Although IIRC the tree froze ages before the release build was rolled.