Another interesting bundle is the Native Instruments Komplete Package(s). I've made the upgrade from "Komplete" to "Komplete Ultimate" recently. It's actually all you ever need, from basses to drums & drums machines, very good pianos and synth - including Reaktor, which lets you built your own synths - as well as the mighty Kontakt sampler, that comes with fantastic libraries for anything, like orchestral, world and cinematic stuff. And there are fantastic tools for mixing, whole channel strips from different ages. And you get guitar rig, which is on its own cool for FX. And there's so much more in there... but even the smaller package comes very feature filled at half of the price.
A lot of stuff in there, but most of the plugins can be used out of the box. If you consider the price and the quality, it's a fantastic value. If you use the possibilities, you won't run out of plugins anymore. Once a year, the company sells everything for Komplete (even the bundles themselves) at half of the price. Somewhere in summer I guess. Maybe worth waiting. (Btw: I don't work for them, just like their stuff :))
Other than that the idea of renting the Slate stuff is definitely top.