Go for the sounds. At this stage, you don't really have any logical reason or need for a bucket seat. For me, Racing seat is part of rational modification for cars...if you're not racing or the car's not fast enough, then why put one. Same concept as those big ass guages like tachometers, why would you put one if there wasnt any significant change in the engine's cut off?
So i guess you wont get any critics if you go for the sounds first, it's a safe bet. (I'm not really a big fan of car audio setup btw, haha)