Bernardwong, I have had great results running my HW-19 with the SDS. Given the age of my table I took the approach of upgrading the platter, arm, and cartridge, and when I wanted that final "push over the edge" (as Nigel Tufnel would say) I purchased the SDS. I can't say it made my table sound like a brand new, SOTA, $10k+ system, but it did make the noticeable improvements noted by Rushton above.
Speed Box for turntable
My turntable is VPI Junior (upgraded versions) with alphason tonearm and Denon DL-103 cartridge. This set up is used for years. I would like anyone who are VPI fans and have the use of VPI Speed box or other brand's speed box to tell me what is the difference in sonic performance before and after the introduction of the said speed box.