If you think about you will acualy not make much power at all ... with a twin set up you basicaly have 2cyl running each turbo ... they will take for ever to spool and won'y make any power ... with single turbo you have all 4cyl running 1 turbo which will cause faster more powerful spool and make more power ... twin turbo only work good on V6's and up.
You may benefit slightly from a sequential twin turbo, but only in response and not in peak power. With a sequential setup you'd have one smaller turbo at the front which spins up faster to reduce turbo lag and a larger turbo farther down the exhaust which would spin up more slowly but provide larger boost. They could both feed one single intake piping.
But if you want better throttle response or less turbo lag then get a supercharger instead. Because you won't get the same peak power with a sequential twin turbo because the first turbo will create some backpressure and rob the larger turbo of exhaust pressure which spins it up to create the boost.
Or if you have infinite money to burn you could just rebuild your engine, go with a huge single turbo and then do nitrous. I dont think anyone is running that setup on the K series yet so you could be the godfather of that setup! Keep us updated on what you choose! :tonguegri