Hi, Richard, and welcome to the club. Here's a little Gear 101:
Most guitar and bass amp combos and heads are actually composed of a preamp and a power amp. I believe your Genz Benz 900 is is just such an amp. You can also have a separate preamp and power amp. Your F-1X is a stand alone preamp. You need to mate it to a power amp, and then to a speaker cabinet. (Although, your F-1X does have a direct out that can go straight to the PA, but let's leave that for Gear 102). On some amps with a effects loop (like your Genz Benz), you can plug into the return of the effects loop and just use the power amp section of the Genz Benz. I don't know if this would work with your Genz Benz and strongly suggest you research this before trying it so you don't fry anything. Otherwise, you will need a power amp. If you give us an idea of your budget and your playing situation, there are lots of folks around here who can advise you on your best options. Once you get it all together you will really enjoy your F-1X. It's a great preamp.
Bill, the guitar one