The travel depends on the a arms and how long the shocks are. PEPS, Ohlines, Elka, ect would do a great job but the most important thing is that its serviced regularly and vavled properly. If you really have money to burn it would be best to get brand new shocks from the factory. If money is limited then go for pre 09 yfz450 or any year trx450r "piggy backs" (there fully adjustable apart from high speed compression) and for the rear an ex400 shock will work well but you will need bushing that Ken O'Conner makes and you will need to remove the airbox lid.
400ex rear shock with the bushing is supposed to be a cheap upgrade for the rear. You wanting wider a-arms? Long travel or stock travel? Like they said, make sure to get the shocks set up for your weight, a arms, and riding style.