Yeah I have coilovers, 17*7.5" rims with 235/45R17 Bridgestone Adrenalin tyres, RDA grooved and dimpled front rotors with EBC Red Stuff pads and UltraRacing suspension bracing in the rear of my car. Coilovers make by far the biggest difference, I noticed that I went from always getting lots of understeer when cornering hard, to the car now holding very well through corners, at times I can even if I try induce some oversteer in the rear... You can choose what height the coilovers sit at so a 30-40mm drop from stock height will be ok on highways and crappy roads. To date I've only found one or two speed humps I marginally scrape on and haven't had any dramas on the highways or average unsealed roads around here....
If you cant afford better rims then just wait until your tyres wear out and get something like a kumho KU31, they are pretty cheap even in the 215/45R18 size, but they have much better grip than stock Yokos plus are alot quieter.