I have one and like it a lot. It has more clarity than the Alembic F-1X and more EQ range than a Demeter VTBP-201. The Demeter is still my favorite but the Aguilar is a great preamp too. Chuck
I have one too. It is awesome. Nice thick growly tone but still detailed and hi-fi- not muddy at all. I wouldn't pay $1000 for it (current street price new) but if you can find one used for under $600 I say go for it.
I own and use one. Mine is currently racked with a Stewart 1.6. Despite its rather low output, the preamp sounds very good; a nice combination of low-end warmth and modern, upper-register extension. Good ergonomics and easy to use on a gig, too.
I used to have one and loved it, but I sold it to get a 680 for a much more detailed, chewy sound. Not to mention the flexibility... oh, and i'd describe the 659 as clearer than the kern or alembic, thicker than the demeter, but not as heavy in the mids. Sounded a little "scooped" to me.
Mind sounds good, but I have no idea if I'd like something more. ??? On www.basstasters.com, most of the sound good to me. So I'll just keep what I have I guess.