JK,
Save up for a Hammond-Suzuki XK-1. Click here for more information. They are brand new, just got a raving review in Keyboard magazine. In summary, it has the same sound generation engine as the XK-3 (which I am now using as part of the XK System and I have retired my B3... I do not miss my B3 at all playing this new digital organ) but less of the bells and whistles. It is light (under 40lbs) so you can gig with it, the onboard Leslie simulator sounds great so all you need is a powered speaker or an amp/speaker combo of some kind, and it sounds like a B3. I think they retail for about $1500. That seems like a lot, but the instrument will serve you well and unlike an M3 (which is a great organ), the XK-1 is lighter, more reliable, and has full bass.
Again, I have retired my 1958 Hammond B3 that I gigged with for 10 years, and I'm now using the XK System (based around the XK-3 keyboard... the XK-1 that I'm recommending to you has the exact same sound engine). It weighs 300lbs less than a B3, but you cannot tell the difference. I have it going through a real Leslie (a 1960s 122) but the onboard Leslie simulator on the XK-1 is supposed to be very good. Go to your local Banjo Mart (Guitar Center) and see if you can play one.
Hey Jim.... Thinking of selling your real B3? I don't know, but it must be something. I want a full B3 organ to play with at home and to take to some gigs. I mean, if I can't bring a B3, I could always just bring my keyboard, which I am satisfied with the organ sound on it. I can't really make any decisions before I actually play the XK-3. Does it have a stand, or is it just a keyboard. I can only find pictures of it, where it shows it from the face down.