unfamilia,

the idea that two 1,000cc engine turbo's are good for an A12 or A14 or A15 is the wrong way to go thinking things through.

There are a bunch of things involved in turbo selection not least of which is understanding the airflow capabillities and characteristics of an engine and matching it against some compressor maps for a start.

I would begin by pointing out that you usually pick a turbo size by first describing the engine it's intended for. This importantly includes size. A 20% increase in capacity(going from A12 to A15) is a different pair of turbos / turbo spec.