it seems you are looking to keep the car as a comfortable daily driver...or i'd suggest a serious gutting of the car's interior and taking out the a/c system if it has one (makes it much faster and nimbler...basically reduce weight and any car handles better)

it also depends on how serious you want it to be a fast car...you can do the myriad of bolt ons to the dx (intake, header, exhaust [i/h/e] and it'll be a little faster...you can swap on a sohc vtec head (d16z6 or y8) after converting to mpfi and get near 130 whp with good tuning and a vafc