walk around 240sx coupe CAI and exhaust

i bought my 93 coupe for 3600 only put in CAI after buying it and now im wondering what other people think would be the best move. i am painting the car midnight blue and thinking black rims with lo pro tires i pretty much know what i want as far as cosmetic goes but just wondering how to get more performance and if its worth buliking up a ka engine or better to just swap for a sr20det..