I'd go the rear disc brake upgrade. Then start on performance. My first car was a paseo. I did the 4efte motor upgrade with a couple of extra mods like intercooler, pod, exhaust etc. I flew! It ate v8 commodores, falcons, everything! Got away with it all for under $2500. Now i have a sera. I've spent about $5000 on the 1.5L and i should have 200kw. Depends on how much your willing to spend. :D