There are Japanese Hifi enthusiasts that use upwards of 7 pre's in a chain... so it's not such a new thing.
The most expensive system in the world, uses 3 or 4 in a chain I believe... (It's a 5 million dollars system I believe..)

There is an article on Lyra Connoisseurs main man Bjorge visiting this guy somewhere on the net.
But for using this on the cheap...
You can also use layered loops in a computer to emulate equalizers.
This could be done in foobar, or even a mainboards own MPU. (I've done it on an old computer ages ago..)
It will sound quite good, but all it is , is distortion, granted, that is all it is!
However... when you want it to sound as good as you can, sometimes, the right type of distortion isn't so bad
after all!
Why does seperates sometimes sound better than a one box solution?
An equally good question!!!!
So, what am I getting at here...
Using devises in a chained up way, was originally used to improve upon expensive systems!!!
Imperial