Patricia brings up some great questions. It really depends on those answers.
Assuming your home is average, based on current properties in escrow, I would expect your home to sell for about $365,000-$380,000. With the studio addition, assuming it is permitted, you might be able to get somewhere around $415,000-$440,000.
Of course this is just my opinion, and other factors that I may be unaware of do matter. The other thing that is going to affect the value of your home very soon is the new foreclosures that are due to hit the market. I can give you that stats and a map of them if you like. I would be happy to speak to you about the different factors that can help your home sell faster and for more money, even in this brutal market. Check out my trulia profile and my most recent testimonial from my last sale on my profile.