Turbos/SC ARE the replacement for displacement. Imagine diesel-like torque in a gas engine?
Imagine a very tall and FLAT max torque curve? Plus, while out of boost; just driving along getting great economy. Imagine the FIELD DAY turners will have with a factory-boosted engine? I'm thinking a simple tuner = 40-50hp at the wheels. Figure I/H/E + Fuel and Tune? 100+whp. I love that. Without cracking open the engine. Oh - and those at highter altitudes won't suffer like they do with Naturally-aspirated engine, because boosted engines (sort of) make their own atmosphere.
Think of it like this: My previous DD, Subaru Legacy GT, made more torque from it's 2.5L than my 5.4L Expy makes. Sure it cost about $2000 in bolt-on upgrades, but wow.