Originally posted by adamwv I've seem some pictures online that are insane zoom.
Aahh, so you mean magnification?? Because DFA 100mm and the other modern Pentax macro lenses all go to 1:1 macro, which is really great. Same thing for the competition (Sigma 70mm, Sigma 105mm, Tamron 90mm), Not long ago, macro lenses could only reach 1:2 without extra accessories (the Zeiss macro lenses still, despite being considered really great lenses)
Lenses that go beyond 1:1 magnification are actually enlarger lenses. They are generally more difficult to use and have many limitations. I don't think there are any currently in production for Pentax, but you can get them only from specialized producers (Rodenstock?). Its a very niche lens, unlike the DFA 100mm, which can be used for purposes other than macro.
Anyway, one thing to keep in mind is that "macro" is not "zoom". Macro is actually "close focus". So to get the most macro, you need to turn the focus ring on your lens to nearest focusing distance (away from infinity), then simply move as close as you need to until the subject comes into focus. That gives you the highest magnification (which is generally considered "macro" when it is 1:2 up to 1:1).
So I would suggest you work on this technique at first. Come as close as possible, use aperture f8-f14 to get a wide DoF. Use tripod and 2 sec timer if possible. Or a flash system for moving subjects like bugs.
If this is still not enough, you can shoot raw and crop the photo in post processing. Cutting the corners off will make the subject seem more magnified. This is a wide practice among macro and wildlife photographers, where the most important thing is getting good focus, and then the framing gets done in post, later.
Other options are to buy a Raynox macro filter (Raynox is a good brand of macro filters; many others are really bad and have low image quality). You can also use extension tubes or try reversing a lens with a reversal ring. There are many ways to get beyond 1:1 macro and there are some threads in the forums here. I think one is called Macro at any cost, another one is something along the lines of Dirt cheap macro. Just look over the macro forum for big threads.
Because the DFA 100mm is.. just about as good as it gets, at least in the 90-120mm range. You can get exotic monsters like
200mm macro, but it will still only be 1:1 magnification - only you will reach it from slightly further away! You can get something like DA 35mm macro (not FF, but great lens), which will still give you the same 1:1 magnification, but a different field of view, and you will have to get much much closer to the subject, almost touching it, to achieve that magnification.