I recently looked into this for compression, however, you are requesting plugins in general. Maybe more specifics would help us help you.
What host/daw you using?
Do you want effects in the mix?
Do want plugin instruments?
What do you want to achieve mastering?
Maybe a good quality external compessor is more use to you?
What are recording?
While waves is reputeably the main stream 'name' standard and good at what they do, they are not the ''be all and end all''. Waves do not and have no intention to support x64bit in the immediate future. They charge a lot of money yearly for updates (not upgrades) just updates. They sound good I agree but there are many other that do a good, if not better job.
As mentioned try some demos.
Personally I would recommend (commercial) :
Sonalksis (soon to have x64bit support and VST3 planned),
De La Mancha (Cheap and very effective),
Fabfilter vst3 already supported.
PSP Audioware products
Native Instruments
Others I do recommend from experience :
Voxengo (take a look at elephant).
Izotope Ozone4 and channel strip
URS
UAD
Soundtoys (Great quality plugins and not over priced imho)
There is loads of freeware again what I personally use and I promise you there are many articles comparring what I am about to share with you to waves (some believe better or as good as waves)
Variety of Sound <Bootsie is an amazing guy with a heart of gold for the work and generosity he gives in his plugins> Worth checking out before you buy anything.
http://varietyofsound.wordpress.com/downloads/
Antress (Not so hot but the tools are still great and may suit your needs.
http://antress.er-webs.com/
Here's some links to take you into the underworld of plugins :
http://www.kvraudio.com/forum/viewto...light=#3181911
http://www.kvraudio.com/forum/viewtopic.php?p=3321417
http://www.bluecataudio.com/Products..._FreewarePack/
http://www.dontcrack.com/freeware/so...s/plugins/VST/
http://hem.bredband.net/tbtaudio/
http://elektrostudio.ovh.org/index2.php
http://kunz.corrupt.ch/?Products <Tal not much I dont use here in productions on every track
>