Manley Signal Processors
Another essential for your audio rack is an equalizer, which Manley also comes through on with some great options. The Pultec EQs are great for starters, and if you really want the best of the best, there's also the Massive Passive Stereo EQ. This beast of an EQ comes in standard and mastering editions, and uses a specially-designed passive setup that links the gain and bandwidth controls to guarantee repeatability.
Naturally, if you're building a road rack or you're simply looking for the most efficient way to get things done, you won't want a whole stack of signal processors in your rack. In that case, the Manley VoxBox is the perfect fit. This all-in-one combo unit packs a mic preamp, compressor, EQ, de-esser and limiter all into one unit. It gives you a ton of functionality all nicely wrapped up in a single box.
Whichever type of signal processor you're looking for, Manley is an excellent choice - and, if you like, you can just go all-out with the VoxBox. They're a highly-respected name in the signal processor business, and for very good reason. This is hardware that you'll know you can count on through every set.