wow i cant believe u got that much for it...man i bought my car about a yr ago for much much much much much less then that and its a 2001 haha. thats awesome but in my area they definitely go for much less than that
as far as the next car, i say go with the s4, they're amazing cars...but its a biased opinion as i own one
otherwise, if buying a bmw id go with an M3
good luck with the next purchase and let us know what you decide on