8″ fresnels are adequate for a 50′ throw, but you’ll have to keep them locked in the spot position. A current Arri 8″ 2K will throw around 85fc @ 50ft in a 10ft circle. I would say you need at least 50fc for most things, so opening up the fixture a bit would probably give you around a 16ft circle @ 50fc. Blending four fixtures together nicely is only going to light you a 24ft wide strip.
I would be more concerned with where/how you are going to plug in 2K fixtures at 16a in random churches. I would stick to 1K fixtures that you can double when possible or separate when necessary.
If you want to go cheap, I recommend just going with basic par64 cans. No need to swap lamps around at that distance. Go with the slightly stippled/frosted narrow lamp (NSP) instead of the clear very narrow (VNSP) and get yourself some 1/4 and 1/2 diffusion to vary the spread.