Should I trade my 2005 Scion for a 2008 Scion???

Well, I have $12,000 left on my car loan but I'm not feeling my car anymore. What I do like is the mods on the 08 Scion and I think I might want to trade it in. Would this be a dumb idea? I was thinking about trading the Scion in for a mustang or Altima also, but I'm really leaning towards the 08 Scion...would I be wasting money!?