Build Your Own on BMW's website requires you to add the Premuim Tier package to the 330i, which is like another $4700, to be able to add the $900 H/K stereo.

I could have sworn you used to be able to add the H/K stereo by itself (without coat-tailing a crazy expensive, pointless content package).
Can anyone confirm or refute that?

The 340i comes standard with the H/K stereo but not the Premium package, which tells me the H/K stereo doesn't depend on hardware that comes with the Premium tier.