I owned a 2004 STi and now own an '04 Red Line. If you're talking about a financially good move, stick with what you've got especially if it's paid off or close to depending on condition of the car and remaining warranty. A new car is always a BAD investment, you WILL lose money. Right now there is very little aftermarket support for the SS in comparison with the WRX but that is changing. The WRX is a great car with a proven track record and TONS of potential (not to mention much better in the rain/snow). The SS is very new and not even much faster than a stock WRX. One big advantage the SS may have is the dealer installed staged upgrades possible pushing out nearly 300 hp and still maintaining a warranty. I wouldn't give in to a rush decision seeing as how you've got a great car as it is. You might want to go to a stealership and take one for a spin and call your insurance company. If you wait till the end of the year, you may be able to get a great deal on an SS if you choose to go that route. You really have to look at your personal situation to know what the correct decision is.
Hope I didn't make the waters even more murky than they were.
Hope I didn't make the waters even more murky than they were.