They're 7.5" wide huh? Always thought they were 7". The Subaru site says 7.5" too. hmmm, even better...
Anyway, back to your situation, get the best quality tyres you can arrange, even if it means getting parents to chip in - safety first

Wider tyre means (to a point) wider rubber and more grip on those occasions when you need to emergency stop.
Your current tyres (if they are still useable and you are happy with them) will also fit on the new wheels so you don't necessarily need to shell out for new tyres straight away.