tire ratings and size on s14

[S13S14S15]

so i have been spending a lot of money lately on my s13, and my s14 needs new tires. so i went to pep boys and tried to get the cheapest tires. then, they told me that the s14 needs at least V rated tires, which are pretty expensive. and they said it's illegal to put on anything less than a v rated tire on there and they wouldn't do it.

so my question is, would it really matter if i got s rated tires on there? also, can anyone tell me what's the widest tires i could go on my stock rims? i currently have 205/55/R16 stock Toyo ones on there right now.