Is the Benz-Micro SLR Gullwing MC a good choice and is it the right one for my preamp/turntable?
Unfortunately, the only one who can really answer that question for you is you. Other folks will tell you what is right for them, but what is right for them may or may not be what is right for you.
In my opinion though, that would be too much cartridge for your table and preamp. I don't know that you would get your money's worth out of the SLR unless you are also planning on upgrading your table and preamp too. In my experiences, the best systems are well balanced systems. Pairing an expensive cartridge or speakers with inexpensive electronics usually does not provide optimum performance. Of course, as usual, YMMV.