you are probably only going to find offsets between +35ish and +45ish for the 17x7s, which will look ok i guess.

for the rears, a +30 offset is about flush with the body. so if u go lower, it will stick out, if u go higher, it will be a little more inwards. about the tires, i wouldnt go wider than 255/45s

just keep in mind that unless you have crazy power, staggered wheels will make understeering in s13s even worse. one of the only s13s to ever make it to the autocross nationals in STS last year was riding 17x7.5s all around (the rules limit you to 7.5" but the point is that he had the same size wheels front and rear). but if you are going just for looks than it doesnt matter.