I converted my OBS to discs and I've got to say that your money would be better spent on a swap to the 11.4" WRX front discs with good pads and a fluid flush. It's easy, only requires the new larger rotors and the caliper brackets. It will only run you a couple hundred dollars at most if you get the cheapie Chinese rotors from Autozone that work just fine.
The rear swap is great for the looks but My 2001 Forester L with drums stops every bit as well as my 2002 with discs. Both have the WRX front swap. Unless you are pulling a trailer in the mountains for the extra fade protection that the rears give then there really is no need for the rear swap.