Thanks! 
I love Rainer - super swish and nn Rainy is so sweet!
I’llet you know if any more pop in my head, but a quick riff: Torin, Rylan, Briar, Starling, Rowan, Meadow, Solenne, Rhodes, Seren, Tierney, Quinn…
I also love Lumi, Eisley/Isley, Imogen, Tindra, Lisbeth or Elspeth, Gwyneira/ Gwyneth, Willow, Delphine, Cressida, Leonor & Bryony - not unisex but has the same vibe to me as Arden. I also heard the name Narcisse the other day - probably unusable but I like the sound.
Would it help to know country? Or not? (Am non-US too.)