A single Radion is definitely going to be two small for a 4' long tank, you'd definitely want 2. So that would put the G4 into more pricey range since you'd need 2. The A700 should give you the spread that you need, but having 2 "point" sources where all the light is coming from you'll get some shadowing on the outside edges of rockwork which is something you wouldn't see with T5s or metal halides with big reflectors (assuming you were using this as lighting 7 years ago). So that also is something to keep in mind when thinking about what you are planning about doing inside the tank. Other options too is to get even more LEDs, just maybe different brands that are a bit cheaper then you could get over lapping cones of light ... but yeah, LEDs as great as they are do require you to think a bit more.