Billy and Bajan have given you some good advice about UAD ... with the current promo, now is a good time to get new UAD hardware.
A few other UAD plugins that I've been impressed with:
Millienia EQ - very rich and smooth with awesome low-end control
Ocean Way - most convincing room sounds I've heard
Manley MP - great for shaping sounds, very useful on single tracks as well as 2bus
Shadow Hills compressor - subtly adds a polish to full mixes when used sparingly
API EQs - sound just like the real thing!
EP-34 Tape Delay - so silky-smooth
UAD plugs are expensive, so it's best to demo them before deciding what to buy. The demo scheme is cool, though -- you can turn on any plugins in a 2-week demo mode at any time, and when you make a purchase, everything is reset so you can start more demos. You could theoretically keep using things in demo mode indefinitely, as long as you buy something every two weeks. That might get expensive, though.
As for Waves, they do have some plugins that I like a lot, including the new RS56 EQ, the H-delay, the Vocal and Bass riders, and the SSL and REDD console emus. But their controls tend to be jumpy, not smooth like other plugins. This may just be a quirk of my setup, though. You can also demo all their plugins, so again, try before you buy. Have fun!
Cheers,
Eddie