Infinity F.E.T. preamp

I am getting up in years and don't spend the time listening as much as I do playing my drums and guitars. I have an Infinity F.E.T. preamp (blue) S/N 173. It has a slight background hum and I am not inclined to put money into it. Anybody have an idea what it might be worth as is, or will it be worth getting all the bugs worked out prior to selling?  I'm torn because I have yet to hear a better preamp (yes it blew away my SP-6). I now run a Marsh Audio P2000., because of the hum issue in the FET. The Marsh is close in character, but just doesn't do the sound-stage quite as well. Now on a limited income I face reality. The Marsh is close close enough to my old ears, and I hope to pass the FET off To someone who will really appreciate it.

Thoughts?

B