The floppy uses a smaller power plug and usually they're branched off from one of the exisitng 4-pin molex connectors. So you still have all 4 to use. It's ok. I have the same amount of molex connectors too. I don't even have the SATA one, lol. I've got an old PSU and I'm thinking about upgrading to a new one because it cuts off on me on rare occasions. Never happened before until I got that 7800GT video card in there. It draws a lot of juice. I can hear the PSU whine when I play NBA Live 06. Big time whine.
So you'll be using one molex for burner, one for HDD, and the rest for fans and video card (if it uses a separate power source like mine). Yeah you should have no problems at all. Fans don't draw a lot of juice. You can have 2-3 fans per molex if you want to. I have that config now. Works great. No problems.