Longhairedhippy, It depends on how much you really want to spend. The top of the line intake, according to most, is the GruppeM. It's made of carbon fiber and is installed within the engine bay unlike Dinan which is routed through the fender. Also unlike the Dinan, GruppeM doesn't recieve the air from underneth the car, but from a small opening by the driver's headlight, of which, it's hard to tell how it really performs better than the Dinan. The GruppeM can be bought from a few places. I believe that Technik Engineering is there official? seller.
Technik Engineering
Look under Powerkits...Stage 1. Includes the intake and chip with a claim of 14hp increase.
Cost....$1195 (incl. $400 chip)
ModBargain has the intake alone for $535. Mike from Modbargains sent me an email with a sample vid of the intake installed:
GruppeM Video 5847.1K.
Now, if the GruppeM is too expensive, which I totally understand, there's also reproduction models out there. They are greater than 10% different than GruppeM to ensure non patent violations.
Umnitza has one.
Now, there are of course other intakes out there. I don't have any clips of those, no one that I've known has recorded them.

This is Conforti's intake. Coupled with the shark injector, gains are seen between 17hp and 21hp, with torque from 8-17lbft depending on how you read thier graphs. Those are thier claims. The photo is from
M3Motorwerks, they have this one priced at $358.95 with out a chip, that'll cost you another $400. It takes it's air from the same source as the stock intake, however, with a more freely flowing system. The filter is an ITG foam peice.
Well then, I've written way to much. There are of course other ones out there, like Benfer and ECIS (which sounds the same as the modded GruppeM variation). I have more clips that I've collected from various forums and places. Just can't find them on my harddrive right now. Hope this helps in some way, and just know that all information is from the dealers site and comments made by others. I don't own any of these intakes, I honestly can't afford anything for my car.
Dough