Did you mean to attach a sound sample? You mention one, but I don't see any way to get to it.
As for strings to try: Worth brown, D'addario Nyltech, LaBella pro series..... Actually, if it comes with those really bright Aquila Nylgut strings, about anything else should warm it up a bit.
That said, maybe you'll actually grow to appreciate the brighter sound as something different from your other ukes...the spruce top is going to contribute a lot to that different sound I'd say.
I hope you enjoy the new uke. I saw your other thread on it and what a great deal!