Ken-
I had a similar situation develop with my SL 900..mine was in the same batch as yours and came from Rocket Music. Both Greg and Jeff were very responsive and I spoke to Jeff Genzler in person late(after normal business hours). He even called back with follow up questions and shipped overnight to me the following business day, promising no problems. After two weeks I can say there have been no probs and it is every bit as great an amp as people have mentioned here.
FWIW I like it with the P, J, and my classic stingray..have my gain around 1-2 oclock and pre volume hovering around noon, cut the bass and treble(slightly), boost the mids to 2 oclock. I actually played a lot with the mids yesterday and love switching from 220 to 600, depending on the tone required. For me the mid boost tends to stay set at 220. At 600 it worked well with the 'ray, adding some bite without clank. I added a tonehammer to the jazz to fatten up the mids a bit but it sounds great straight with a P and with the MM...
IMO of course
Mark