Have you also considered ebay consigners? There are a couple big card consigners that won't require grading like PWCC, Probstein, Dc87sports etc. They take a commission on the final value. The higher the closing value, the lower the commission. High value items like this get listed quickly, especially when you want to have the item sold during the NBA Playoffs to coincide with the typical peak of the card marketplace (cools off in the offseason and winter). I don't have experience with any, but you'll find reviews on other major card forums.