Current gen Dell XPS (not the z model - 15z) may be your best choice with JBL sound. The sound system is amazing. The 15z, though it looks sleeker than XPS 15, will perform weaker in games and weaker sound system.
I also own an HP i7 with Beats Audio, and it has great sounds too (and it has a fingerprint reader unlike the Dell). Third, I'd say Toshiba Satellite with Harman/Kardon speakers. Watch out for Toshiba Satellite models - many don't have discrete graphics so you can't play any intense game at decent settings.
Since you're going to do some sound work, I only mentioned laptops that I know have excellent sound systems based on experience. I'm sure you'll use external speakers, but in case that you won't then you're covered if you buy any of those three.