Yes, make him take a test ride with you. I've tried preaching to him about waiting on the suspension, spending the money to do it right, and not regretting it later. IMO, some good adjustable coilovers >>>>> a shock/spring treatment. Feeling the difference in a MKIII supra with stock, one with spring/shock and one with coilovers was night, day, and a whole 'nother week. The coilovers handled better than the spring/shock and rode nicer than stock plus they were adjustable. Far worth it in the longrun and you can always have them rebuilt down the road when it's time. Also, the coilovers are more matched than a many spring/shock combos. Also, keep in mind, just because your car is low and stiff doesn't mean it handles any better.
Shit, forgot to mention the sways. IDK if they make as big of diff on WRX's as they do on my car, but they are HUGE improvements for the money. Again, I dunno how much some good ones are for the WRX, but ours are pretty cheap. Best bang for the buck on upgrading the handling in our cars.