Hi TwistedRoad,
If your wife is 80% happy after only two weeks then I would be very cautious about adding 3" of ultra soft latex to your mattress because of the risk of potential alignment issues. There are also some suggestions in post #2 here that may be helpful.
If you do decide to add a topper then post #2 here and the topper guidelines it links to has more information about choosing a topper that can help you use your actual sleeping experience as a reference point to choose the type, thickness, and firmness for a topper that has the best chance of success.
Phoenix