ken,
our coupe stock engine are capable of handling extra boost, as the engine block are of iron cast which is the same material used on Skyline. There are people boosted it up to 250HP with no problem. To play safe, a boost of 0.7bar is good enought already and get you to 210HP (around there). Its the cost whether you have or not.
EVO engine are expensive to maintain. You have to swap the gear box as well as only the gearbox that comes with it are capable of handling its power and characteristic. I would say it gonna cost you up to RM15K for a full swap in.