I am currently in the process of replacing my rattly-ass stock twins. As far as cost, yeah, it's a no brainer really. A pair of new OEM twins is as little as $1200. Pure or Dinan stage 1 are both under $2k. Pure stage 2 is under $3k. And installation will be between $1-2k. So $2500 out the door for the cheapest option.
For me, the key thing was separating what I wanted from what the forums told me I wanted. I fell in love with my car for the lagless boost at all speeds, so my first priority was retaining that feeling. I don't need 700 hp; the thing can barely grip the road as it is. And my second priority was having a redesigned wastegate that wouldn't rattle. I'm hoping I found the solution to both with Pure stage 1, but we'll see in a couple weeks after it's installed...