Although in my opinion effects can make the harp sound arbitrary, here are a few other effects.
Lone Wolf Harp Octave
Does not really sound like an Octaver. More like a distortion pedal. Sounds pleasant. No need to think about levels.
Although the harp sound is gone, now you have an organ. Sounds good, and there are certainly lots of ways to use.
BBE Sonic Stomp
I own the BBE as a pedal and 19" equipment for the PA. It is a kind of loudness .... The 19" hums and the pedal .... sizzles a little under load. Not a must have.
If you need a special effect, you know what you are looking for and specify the search. I think it makes no sense to buy choruses, compressors, tremolos, Envelope Filter .... just for experiments.