I think baker is saying that waiting and researching it will make him happier. Maybe he has the cash for a Z6 now, but if what he really wants is a B series, then he should wait. Otherwise he's going to spend the money and time getting the Z6 in and maybe not be happy with it, and end up losing money when he goes B later on.
As John said, 2 grand isn't going to get a B in there, at least not a reliable setup. Now, if he sits on it and waits, collects parts and gets good deals, maybe, but then he is waiting again!
Personally, unless you already have a B17, I don't know why you would search for one. It will be a lot cheaper and easier to go with a B16 or 18 in the long run, since they are a lot more common. If you go with a B16, you may as well spend the money on a Z6 or another D series (maybe a DOHC ZC) and build it up a little, you can have a reliable D that will make the B16 seem slow.
I have been through this myself, and I say wait and plan it out perfectly. When my A6 blew the headgasket, I was considering a few swaps. Eventually I realised that I couldn't afford to put together a decent, reliable B series, and I didn't want to go with another D. For a couple hundred bucks I rebuilt my A6, and I loved it. I had a good 6 weeks to do the research, and when I did the rebuild I had everything ready to go.
When the A6 threw a rod, I was in a rush, and I put together the motor I have now, A6/Y8 mini-me with PM7 pistons. I had everything on hand, but I didn't think ahead enough to get all the tuning stuff, and I had to run on a stock P28. It sucked. Even now, with all the parts I need to tune it right, it still is giving me trouble trying to tune it right. I also did a bunch of stupid things trying to get it going, since I wanted it done IMMEDIATELY after I pulled the blown motor out. I'll be rebuilding the bottom end this week, and most likely going back to my PM6 pistons for now, and building a separate motor with the PM7s. I just want a reliable, properly working setup, and I can build the other on the side.