Never been a big fan of Ksyriums. Depends on the model of course, but generally DT Swiss hubs are superior to what comes on the Ksyriums. But since you got the frame cheap, I might suggest you splurge on the wheels. A good sturdy handbuilt wheel-set from a reputable builder will be fast yet have the durability you need as you continue to work on your fitness.
I've never been in a position like this. I have built wheels myself, but usually with used hubs, new rims and spokes, and settling for strength, not lightweight... I may still grab the DT wheels though, I can use them as spares for my other bikes!