I need to buy at least two new tires asap. Didn't notice that my alignment was off and my front two OEM Toyos are about gone.

The back two are fine, so should I get just two new tires or go ahead and buy four? If I get all 4, Costco has a $60 coupon.

I've been shopping around and it seems like even the cheapest tires will set me back at least $100 per installed w/ all the trimmings (road hazard policy).

These new Primacy tires seem to be getting great reviews and will only cost me $140 each with Costco's lifetime balance/rotation/road hazard/flat repair. Or $125 each if I decide to go all four.

Any advice?