Does anyone have an idea what Sansui B-1 in excellent condition is worth?

If you can't find the Audiogon Blue book value, try asking on audio karma, or audio aficionado. They're more geared towards the vintage market.

Prepare yourself for the fact that "rare" won't always equal high value...or even good performance. The fact that it is rare means potential buyers will have a hard time learning about its strengths, weaknesses, and parts availability. I would assume the "pro" audio nature could be a turn off for some buyers...but you never know. You might just find that one Sansui hoarder who has to have this piece is his/her collection. The auction site would be your best bet, since the masses there pay stupid money for all kinds of things labeled "vintage, rare, and antique."

Really interesting amp. How does it sound? I havent seen one. I think unless you find an enthusiast it would be hard to get more than $400 for it but that's really just a guess.

A few things to consider: 
- 80s power amps arent in vogue right now even among the vintage set. There are some great deals on nice components from this era for that reason such as yamaha m series power amps. This could change in the next few years. 
- this unit is heavy so local pickup is probably best. This could limit your market or price if you ship it given the shipping cost. 
- as noted its pro or semi pro which again puts it into a specialty category. 
- i think it has a large fan? If so many dont like that. 

Amp sounds great! I currently have it powering the high frequency channels on my B&W 808's....exceptional clarity. I tried posting a pic of it, but it won't let me. Someone offered me $3K for it sight unseen, think I'm going to jump on the offer. 

If you get $250.00 you would be lucky good luck.

Hold out for $6,000...it definitely happen.