First off, if you are thinking of trying to get your ds into Davidson Young Scholars (DYS), I'd do the achievement testing first b/c it is usually less expensive. DYS serves the extreme of the gifted population, so your ds may or may not qualify. My girls are not in DYS, but we do post and get helpful information from this board.
If he scored well into the 99th percentile on the composite score on the OLSAT or you have other reason to believe that he is working many grade levels above his current grade (K or 1st), then it might be worth the further testing. In K & 1st, just for perspective, my oldest was reading 5 grade levels above her current grade. She still is not DYS eligible.
Hopefully a parent whose child is a DYS will chime in here soon to give you some personal input regarding the benefit of DYS.
