What Guys Said 1
If all your bills are caught up and the house is in good shape, invest in an IRA . By bills I mean major ones like the mortgage and such. Unless you plan on selling your house in the near future then I would invest it. Or at least by a CD and keep the cash as a "cushion".
What Girls Said 1
ask yourself---is it essential that you upgrade your house?can you live without a car?if you don't need either of those things, then save your money for something else. just because you have 15K doesn't mean you have to use itbut if you really want to buy something, then I would go with a new car just for safety and convience reasons.