It's good to buy the kits if you're just starting out and have no idea what you need....but if you already know what filters/heaters..and accesories you need...you're probably better off getting it all seperate. The equiptment that comes in those kits usually isnt' the best.
I asked about kits at the LFS near my home,PetSmart.
I wasn't impressed with the "gadgets" and asked if I could leave some out and trade up on other stuff.They said they'd do it.I don't need all those chems and the heater.If I did get a heater I'd get 2 smaller than the 1 big.Now I'll be able to upgrade the filter and hood.