It is hard to estimate how much PAR you get with two or three lights that are identical unless they are placed very close together. When you use a mix of different types of lights with unknown spacing it is pure guesswork as to how much PAR you will get.
Ok Hoppy, my intention would be to use 15w Sylvania bulbs or similar quality bulbs. Since i would be looking to use 3 fixtures over a 48" length, therefore the fixture would be in the centre of each 16" section (unsure as to whether I will be using the 8.5" or 10" domes).
Does any of this info help or are we still shooting in the dark?