Speaker/Equipment Placement

"From an audiophile perspective, is it preferrable to have nothing in-between the speakers?"

Definely preferrable, as it add depth to the soundstage.

It is preferable but it is not a disaster if you do have something in between so long as it is not too tall and too close to the speaker to cause major reflection.

I tried a bunch of different setups after moving into new digs two years ago -- equipment in between, equipment rack off to the side, moving everything to another wall and then trying both again. You get the idea. I always ended up enjoying the music most with the rack somewhere other than between the loudspeakers. This may vary if you can get the speakers well off the wall, but as I'm limited to two to three feet, it always made a difference to get the space between them clear of stuff. This has been true, by the way, with four different pairs of speakers and with a few different electronic setups.