Fairly sure KLM allow pooling of baggage weight, so you could buy 2x 23kg bags for whatever the price (If they aren't elite, elite+ or ivory they should sign up for ivory for discount on the 1st bag). That would give you total weight allowance of 69kg over 3 bags which is just over the 64kg of 2x 32kg bags.

Unless anyone can confirm either way whether this would indeed work, you could run it past KLM and see what they say... Maybe they would only allow if you actually checked in 3 bags?