Absolutely worth the money for the cheaper reactors, although I can't personally justify the prices of some of the higher end reactors. The build quality on the pricey models are significantly better and they'll last a lifetime, but they all run on the same basic principle. Running media in an upflow reactor is much more efficient than running them in media bags, so it will maximize the impact of GFO & GAC. Lkewise, the solid carbon dosing pellets require a reactor to work properly because you need to utilize the surface area of each individual pellet and they will merely get caked with detritus if left in a media bag where they can't tumble. If you're looking for a cheap alternative to the pellet reactors, you can use a phosban reactor and just replace the sponges with the rigid plastic screen found in craft stores. The sponges will get clogged up to quickly, but the pellets are small enough to pass through the holes in the retainer discs of most reactors, so you can't just remove them.