Carlo Bonte, from Belgium, sells on 14 June 2017 an "attributed to Sion" Saint Cecilia, estimated at 8,000 to 12,000 Euro.
The painting was sold in 2008 at Hampel as a Peeter Sion (1649-1695) as well, but is now, according to the RKD, attributed to Gérard de la Vallée (1596-1667). I don't know why the auction house reverted to the previous attribution.
RKD. The works are nearly identical (size as well), a major difference is the additional group of angels or putti at the top right, above the door. But otherwise, as far as can be determined from the small black-and-white photo of the other work, I see no reason to attribute the one for sale to another artist. It sold at Tajan for 38000 French Francs, or some 6,000 Euro. It was sold again at Piasa two years later for 29000 French Francs, which is less than 5,000 Euro (I have no illustrations to compare, but from reading the description and sizes, they seem to be the same work).
Frans Hals Museum. It is dated to about 1585-1595, so before the birth of Vallée, and depicts King David playing the harp.
In 2008 it fetched 17,000 Euro (against a 20,000 Euro estimate), so the current estimate is considerably lower.
The 2008 estimate and price seem to have been rather high, the current estimate is in line with what both the other version, and other works by De la Vallée fetch. It is a very attractive work though, and a nice example of how elements of older works get reused in a way we would now call plagiarism (or intertextuality if we were pretentious and post-modern).