Thanks again folks! I enjoy gettin into this stuff when I'm able!!!
The differences among the 500/590/590A1, are few. There are infact more 500's in use as duty firearms than 590's or 590A1's. So dont be put off by a 500 or 590 that doesnt have the "A1" designation. If you like the 590A1 over the 590, then I say go for it!
The wiggle is normal, entirely, and even the wear marks, every gun wears a little differently, but the wear on the 590A1 seems to be more even rather than having "spots" or "areas" that wear more than others.
On the 500 "A" designation, to the best of my knowledge, the designation is as Lazy mentioned, however, I see the "A" used commonly with these Persuader models, as in "500A Persuader". Its something I could ask the Havlins about friday maybe.
This is another of those cases the receiver is stamped "500A" and it may just be a weird Mossberg thing, dont know, but I'll get some clarification.