Strictly speaking the Waves L series are loudness maximizers and not particularly suitable to this kind of application, which I assume is more about dynamic control and also assuming that the application is intended for inserting into the master bus of a hardware mixer to which stems are being fed to separate channels. Even in the scenario of it being just a stereo feed I'd still recommend a hardware compressor over running a plugin live, if not simply because of the stability factor and avoiding that digital garbage that could occur should you overexcite software (ample headroom is all important here). Though any PA worth it's salt should already have a limiter(s) in line for speaker protection, which will respond to both excessive transients and RMS, there's the obvious argument that you don't want to be setting the system limiter into motion either by sending it too many peaks or too squashed a signal. Personally I'm more in favour of higher dynamics in a live situation due to psychoacoustics and the way the ear operates which is quite different at volume. The aim of the game here, again I'm assuming, is not only to provide some control over potential rogue peaks but is primarily to glue the mix together.
One thing is for certain and that is there's absolutely no need to spend that amount of cash on a compressor for live usage; the subtle differences of expensive units will be lost at volume and I'd avoid any that impose a 'character' for this application (unless that's actually something you desire). The most important factors are that of transparency and being noiseless, of which there are a myriad to choose from out there under £500; just don't pick up a used Alesis 3630 and expect it to be of any use!
