New to Preamp - Preamp suggestion around 10k

Hello all! I am new to this site, and preamp. Thiss might be niche, but I am using a Stax headphone with its amp, which has a bypass function for external preamp. I am trying to add a slight bit of warmth, plus better dynamics and imaging.

Currently I have found some good ones (and available), from what I've seen on this site, as follows:

Rogue Audio RP-9

Cary SLP-05 (around 11k with the "ultimate upgrade")

I've also seen ARC Ref 6 suggested, but there seems to be a lack of sellers in my place. As for SLP-05, the distributor at my place said there was no demo, even for the standard version......which left me with RP-9 for audition. Would much appreciate your opinions on them, and any alternatives!

Thank you in advance!