I don't know about your table and tonearm, but if it is like most vintage tables, the arm would not be ideal for a Koetsu which prefers a quite heavy arm with very good pivots (meaning low friction but very tight so they don't rattle). The Koetsu Rosewood would sound very good in any half decent arm, but, it really shows its special qualities when used in the right arm.
Still, if you like what you have already, and the Koetsu does not make enough of a difference, I can see why you would return it. If you have any concerns about having to re-tip or otherwise service the Koetsu, a reconstituted version of the company is back in business and can service the cartridge and my local dealer has gotten very good, fast, and reasonably priced service from Andy Kim (California) who services cartridges.