My 05 WRX is coming up 50,000ks and I want to replace the spark plugs.

I guess I want to stick with original plugs as no complaints so far unless anyone has any other recommendations and why I should swap for a different type.

My question is shall I just get the originals from Subaru or will they just rip me off with the price or can I get them from anywhere and cheaper. Does the gap come preset or wiil I have to check it and if so what is the gap??

Thanks