Mate, you're not giving us anything to work with here.
You basically have a standard car and wanting to put 500 rwkw worth of turbos on it.
Realistically, 20k ain't gonna get close to doing a build PROPERLY like that.
What will you use the car for?
Will you build an engine. If so, how big?
How much are you willing to spend on the head?
Fuel?
Do you mind it being a pig below 5 grand?
Chucking turbos at a setup and hoping for the best will end in very poor results.