I would place Burebista's victory over the Western Sarmatian alliance, see
http://www.kroraina.com/sarm/jh/jh1_7.html
....in the mid 70's BCE.
Torsten
****GK: I don't think there was such a thing as the "Western Sarmatian alliance". I think Appian's "Basilidae" are the Roxolanians, and Strabo's "Basilidae" are the resurgent Scythians. There was certainly no W.S. All. in the time of Skilur and his father, and both Roxolani and Iazyges were their vassals. Previously they seem to have depended on the Royals in Central Asia, and were basically not allowed to cross the Don. They acted autonomously after Mithradates defeated the Scythians, and continued in this way until Farzoi's epoch. But this is a minor point in the context of your concerns.****