Latest news on the matter: They didn't have any condenser mics or preamps at the music store, but were willing to dive into that and order some. Instead they borrowed me a mixer (Yamaha MG06X) to use instead of a preamp. Now I have tried it, but no matter how I adjust the gains and levels on the mixer and soundcard I don't get a satisfying result. It's about the same hiss levels as before. I tried with both the dynamics and the condenser. Maybe that mixer still is a good thing to have, but to get rid of the hiss I guess I need to step up even earlier at the chain - the mic. So I'm gonna read deeper in the forums to gather tips on good mics for harps and see if my music store can order any of them for me to try.
Dave> Yes, I'm using Steinberg's ASIO drivers. I also have ASIO4all to use when the Steinberg device isn't connected. And yes, two mics, or more, is probably better so I think I will buy two if I find any nice ones. Now I'm playing on a folk harp, so it's not as huge as the orchester monsters, but I guess it's still a bit hard for only one mic to manage.
Keeping my hopes up.