SI head on STD engine

Hi,

I am replacing my headgasket in the STD hatch this weekend.
Anyways, I have a spare SI engine with the header still on it.
While im replacing the head gasket i decidied to also in put the SI header on, instead of the restrictive STD header.
However, I do have the complete head from the Si engine.
Is there any advantage to put an SI head? More compression?
Will I gain any hp worth doing?

Also, should I replace the valve cover gasket while Im at it?

Thanks

bigger lift cam. i'd do it if i were you