Going out to dinner sounds good; going to a supper club sounds even better. And that's where hip L.A. night-lifers are heading these days, not to just dine, but have a drink at the bar and listen to live music as well. They're doing just that at Rix in Santa Monica, a multilevel space where martinis and jazz flow all night. The dress code? In a word, whatever--leather pants, faux fur wraps, Doctor Zhivago coats, stiletto heels and L.L. Bean-ish plaid jackets. It really depends on where your priorities lie: supper or club.