I'd probably go with the C-3 in your case - unless you had a front projection system with a projection screen that is acoustically permeable (designed to allow a speaker behind it fire through the screen without affecting the sound). Rear projection or direct view displays are going to be better suited to a purpose-built center channel, and the only difference between the F-3 and C-3 seems to be cabinet size - the C-3, having a smaller cabinet, doesn't have the same low frequency extension, but otherwise should match up just fine. Set the center crossover a bit higher than the mains' crossover and let the LFM-1 do its thing.