The Fostex F200 reminds me of the JBL 2115 and the FW305 reminds me of a 2205, 2225 or 2226. In fact, the cabinet you should use is exactly the same except for the woofer cutout. I haven't used Fostex drivers, but I can tell you that list of JBL's is my all time favorites, so I am pretty optimistic about what the comparible Fostex drivers must sound like.

The Fostex FW305 is best used in cabinets from 1.0ft3 to 4.0ft3 tuned to 38Hz. PiAlign suggests 2.25ft3 tuned to 38Hz, exactly like the JBL's. Put it in a Professional Series seven π cabinet and I'll bet it will sound great. If you don't have corners, put it in the Pro four π cabinet instead.