SKX line of watches

Hi all,
I'm new to collecting watches, and I'd like to add a Seiko dive watch to my collection.


I'm open to buying a used one, but I'm overwhelmed by the apparently almost endless variations. LOL


If I'm right, the two current "classic" models are the 007 and the 009. But there are so many variations and older versions of those two, at least on eBay.


Are some variations of those two models better than others? Are some of the model numbers on eBay fake ones?


If my question is too vague, I'll do my best to clarify it.


Thanks,
BB