chris, i highly reccommend against putting anemones in a tank(different story), but i know for a fact that i would not even be looking into them for at least a year, you have to get your tank well established fisrst,which takes about a year, more or less, and i don't care if anyone knows some miracle to cycle and or mature a tank in a day, you cannot mature a tank enough to keep an anemone any faster tahn that(i say thatbecause i have heard others(not you) say they matured a tank in 1 week with......), anemones are very delicate and have special needs, not only your experience, and don't live as long as they should in an qwuarium(very few people can keep them for even a year and less can for 2, which is nothing)
i would personally do alot of research(not just askin on boards) before even considering one
to answer your questions, percs seem to like carpets, and 1 would be enough for a pair of percs
HTH
edited: most clowns, itis hit and miss whether or not htey will take a host anemone(some do, some don't, no way to tell) but percs will do more than fine without one(esp. if it is tank breed), and many even take to soft corals as well
