I've got my IS200 converted a couple of months ago, and its running well so far.
I got mine done by a LPGA approved installer. He installed a BRC Sequent system and it cost me £1850.
From doing a bit of research before I had mine done, I found that a lot of people recommended BRC or Prins as they are meant to be two of the best systems. Expect to pay anywhere between £1800 to £2500 for one of these.
Also, make sure you get flash lube installed as this helps protect your valves.