The KA does have a lot to offer and a great engine to build from RB25 or sr20 both so different in how they drive and feel a hard choice,i drive an RB25 atm and love it and just hearing it makes me smile and the same with my RB20 before and itself is such a good tuning platform ,on the other hand if i brought a sx also Silvia's in my country i would be happy with the sr20 engine which it came with as i love those engines.My s13 came with a ca18det engine in stock and that was a good engine as well.A lot of folks are going the VH45DE route where i live something which i see a lot of, folks in Japan have been doing for a few years now and adding a twin turbo setup to that.