Certainly, an appraisal would be most desirable in terms of credibility but a good CMA should find you in the same general price range. It's tough to beat FREE...............
I agree with Patrick in that the best way to determine the value of your home is to have a local Realor assist in determining real value by evaluating the home's offerings. While online portals can provide you with an estimated value, they most often are devoid of tbe interior offerings that can make a difference.
In full disclosure, I do not cover your area, but encourage you to consult local agent to get the most for your money.
Most recently, I met with a for sale by owner who relied on what he found online for pricing. I strongly advocated a higher price ($10k), but he insisted on relying on what he found online. He ultimately listed at the "online price" and found himself with an offer in 6 days. I honestly believe that if he had listened to my advised, he'd be $10 richer! Go figure! We're just the realtors!
Love and Peace,
Francesca, Realtor, ePro, SRES