I was intrigued by these recently too. Couldn't find anything on the archive to listen to. I'm guessing the 100-200hz hump is gonna sound fat. The 5khz hump on the card might sound a little shrill on some sources, like running stage lip in a situation where you are getting too much cymbals anyway.
I've read that a few years ago when ADK came out with their basic A51 model, Dave Royer sold a kit to convert it to a tube job.