Transcendental meditation

Transcendental arguments are starting to bother me. They have to start with experience and undermine some other, less inclusive, notion of experience. They do this by reasoning to a "ground" of experience--usually just a broader notion of experience. But the missing thing is given in experience, so experience seems to be presupposed. SW says: for our experience to be the way it is, we have to be given some things noninferintially. And this seems true. But it also seems to flat-out beg the question against Hume or Stroud who say that no such things are given in experience noninferentially. Then there's Kant. He says: look, we do things with concepts, so these concepts must be grounded (bla bla bla intuition, spontaneity, schematism). But it seems that if he wants to get started, Kant has to assume the richer notion of experience, then give an explanation of it. And Hume would just not assume rich experience.

(The degree to which Hume-experience shows up in Kant's explanation of his richer notion of experience is something I'm worried about.)

I made transcendental arguments in almost all my undergraduate annual essays--with the sole exception of the one that was about transcendental arguments. But the essays that obviously reasoned to "grounds" felt unsatisfying. I'm afraid that reasoning to "grounds" leads us to think of elements of experience as forces in a mechanical picture of our relation to the world. I'm also afraid SW's argument doesn't so clearly reason to a "ground," so maybe it's not such a good example of a transcendental argument; or maybe it's a perfect example of one that doesn't inspire mechanistics--even though it seems to beg the question.

How is a transcendental argument not like prefutation, or rejecting one of the opponent's premises?