Trackers that do 14-bit sound on 68000?

[Britelite]

No.
14-bit audio works by using Paula's built-in for free Channel Locking function which locks 2 channels together into 1 channel.  1 of the channels provides 8-bits of data and the other channel provides 6-bits of volume control.  They are fed with the normal DMA mechanism, otherwise it would be quite useless.

That's not actually how it works though, there's no "channel locking" function in the Paula. The trick is to play the highest 8 bits on one channel at full volume and the lower 6 bits and minimum volume on the second channel. The volume control is not touched at any point.

[Britelite]

So....just from a hypothetical perspective then, does a stock 68000 even have the horsepower to do 14-bit audio?

I seem to recall seeing a demo a few months ago posted here on A.org (link to YouTube video) where an A500 was playing an uncompressed WAV off a hard-drive in 14-bit audio.

The 14bit part is not the problem on 68000, but rather what you want to play. Uncompressed audio is easy, and even some compressed formats. But mixing several channels in software might require too much cpu-power.