There is a free alternative for Softube Bus Processor. I own the most plugins from Softube, but they can be really expensive. If you subscrive to there newsletter, you will receive regulary mail with nice offers.
Anyway, I found a nice free alternative for the Softube Bus Processor, named Muchild from Analog Obession. MuChild brings iconic vintage compressor with extra features like side-chain filter, external side-chain and wet-dry blend!