Thinking about buying a different tube preamp...

Don't give up on those Sophias Abucktwoeighty. Their premium 6sn7s are rather pricey BUT they are hands down the most satisfying of all the 6sn7s I've used in my Supratek pre-amp and I've tried virtually all of them. Very linear with excellent extension. This is not to say I haven't had a couple of them go noisy on me before their time. Just make sure to purchase the 1 year warranty. I also have the same result in my Oppo Modwright with the Sophias.

"Don't think......feeeeeel!!!" 🙏

Many vintage 6SN7's from companies like Ken Rad, Brimar, and those silly metal base Sylvanias are microphonic. It's going to be very tough to get low microphony quality ones as we move down the road. The regular Shuguang 6SN7 sounds fine to me. The Russian ones are more durable. I cast a suspicious eye on some current production tubes that are being priced so high. I'm not sure how to reconcile the increase in price.

My inventory of vintage 12AU7's from Mullard, Brimar, Siemens, etc is about 13,000 pieces. My 6SN7 inventory that is TRUE low noise low microphony is about 500 pieces.

The reason is that most stocks of vintage NOS tubes comes from ex-military goods and 12AU7's were used extensively.

I've been doing a bit of searching and have come up with the Northern Electric 6sn7's and the GE 6sn7GTB's for their claimed low noise and extended highs.
I tested my Sophia's on the ancient tester my brother gave me years ago and found one of them questionable.
I like detail and extended highs, with good bass as well. Read about the TJ Full Music 6sn7's that were described this way. So far I'm leaning towards the NE's and GE's.

You should get all of that noise out of your system. Noise modulates with the music and ruins it. Send it back to the manufacturer, but get it done. Too bad