Your center may be your limiting factor there, because with the RF-3s, you should be able to handle a 60Hz x-over. I'd try it out and see how the center handles it; it may be a bit too much bass for it to handle. 80Hz should be OK for your setup though.
You are not completely removing sound below 80Hz, but rather decreasing it as you go beyond 80Hz and the opposite occurs for the sub - though the low pass is generally steeper than for the mains (~12db/octave for mains, 18-24 for the sub). That means your mains will still be getting down to at least 40Hz, just at a much reduced level and with a 60Hz, you can expect some output down to 30Hz. Like I said, try it out and see if you like it and if it strains; if it does, put it back to 80Hz
I got started in car audio as well
