The UAD's will require the Hardware.
While I am a very avid supporter of Waves, I would say
if you have the money, get the Hardware and some UAD plugins.
The main reason I say this is that, since the UAD plugs are hardware based,
they will take some load off your CPU, and are just as good, if not better, then
the Waves.
I love Waves, but their products seem to be very "non-friendly" with Sonar.
I recently dumped Waves, as I found I was tired of the issues with Sonar.
Many have no issues, but I was not one of the lucky ones, and didn't want
to waste any more time waiting for fixes.
As Rush says "Roll the Bones"