Well, on the RS2 that I use quite often I didn't want another Iwasaki built JVC lamp, because they all seem to flicker around 500 hours. They last OK and the flicker will usually go away when run on high for awhile. But depending on who one wants to listen too, that flicker means the lamp is actually gone bad.
Also I didn't want to try an remember to rotate the bulb itself every 500 hours to maybe keep it from happening. So, like whats in the RS2 thread I managed to find a Philips bulb and works fine. Didn't JVC use Philips for the RS20? It appears nobody seems to know who they are using in the last models.
Anyway, I've always just replace the bulb itself in Rear Projection with Philips or Osram when possible. Its usually easier to cross rear projection though. As already stated most times the info is on the bulb itself. Need to know the Reflector type and maybe even the arc gap. Last time I checked Apex was using Philips and that Diamond group someone mentioned, is suppose to only use OEM bulbs. The only think about the bulbs that come in a JVC housing, is they usually don't have a screw on type connection like almost everyone else uses.
So, just have to do that yourself or buy a generic housing. Some of those smell but can just switch the bulb back to the JVC housing.