Cirrhilabrus sp. (fairy/velvet wrasses) is arguably my favorite genus. For a 75 gallon, I recommend no more then 2 adult Cirrhilabrus. Scott Michaels mentions that Cirrhilabrus are aggressive towards congenors, but it's my experience (and several others as well), that two different species can be put in the same tank with little to no problems. However, it's highly recommended that you introduce them at the same time, or the smaller specimen first.
Two conspecific males (and to some degree, females) will fight. However, Cirrhilabrus is completely nonaggressive towards any other species of fishes, including other wrasses. And although peaceful, they will hold their own against aggressive feeders. A genus that does not get picked on, and does not pick on others ... the perfect combination.
A better option is to stick with one species, and introduce a male/female pair. Cirrhilabrus are haremic fishes, and it's ideal to have one male with 3-5 females. Unfortunately, your tank size wouldn't be able to house more then a pair (comfortably).
The readily available Cirrhilabrus I recommend: C.scottorum, C.jordani, C.solarensis, C.exquistus, and C.luteovittatus. All Cirrhilaburs species are desirable, but these are relatively affordable, usually available, and very gorgeous.
Pardon my spelling if any is inaccurate.
Keep in mind to have the tank covered (or at least the canopy). All jump when spooked or mating.
And then there are the other genus of wrasses that are almost as fascinating ....