Stable transfection - how?

[Emir Khatipov]

I am thinking about making a stable transformant cell line expressing
luciferase under control of a custom promoter. The purpose of that is to
eliminate the necessity of making transient transformations/transfections =
to avoid "shocking" cells.  Is there any kit/vector/system you could
specifically recommend for that purpose? The cells I want to transform
already have a hygromicin resistance marker. Is it worth (simple enough)
doing at all?
Thanks for your recommendations.
Emir