On RTAS - then get the MCDSP Emerald pack.
There are two saturation plugs in this pack, AC-1 & AC-2. While AC-2 is a great for tape saturation, AC-1 will give you the kind of saturation you'd get from analog channel amplifier circuits.
So you could insert both AC-1 & AC-2 before a compressor for taste.
Also if you get the the Emerald Pack you'll have really nice collection of plugins. Go download the demos and check them out.
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