Seeking a Warm 12AX7 Tube for Preamp

OK. So I have to come clean... I made an impulse purchase. I've been enjoying THC edibles. And a few weeks ago I got an email about a Chi-Fi option. It is one of those "clones" that's based on a venerable old model who's patent has long since expired. So I bought a unit that is modeled on an old Matisse tube pre. It uses (2) 12AT7 and (2) 12AX7. I bought some new Mullard Reissues (12AT7), and I got a deal on the 12AX7 (new JJ). All from Viva Tubes.

https://www.ebay.com/itm/224885709348?var=523754766478

The preamp is shockingly well built. And sonically it is doing some very nice things. Very quiet noise floor, great open sound stage, and wonderful detail. But tonally, the balance is a bit thin, and the upper mids and higher frequencies are "shouty."  So I'm looking for something a little more warm on the top. 

@trivema I think you might be on to something with the "too much gain" comment. I have noticed that I'm at 90dB spl with the volume control at only 9 o'clock. I found some used GE 5751 that I ordered from an eBay seller with a good reputation. He says they are tested, both sonically (matched) and electrically and are well within spec. Thanks for the tip @mulveling!

Just as a backup, I also bought some new Mullard Reissued 12AX7. So I'll have some things to try out and see if this beast can be tamed on the top end. 

I have to really thank everyone for all of the suggestions. I've read them all. And even if I haven't mentioned here, I have more options from your thoughts and thank everyone for taking the time. I'll have the tubes in this weekend and will post an update after I have some time to burn them in. 

G

The picture of the GE 5751s that I'm waiting to come in look to be gray plates.  The other 2 tubes are 12AT7 and I have Mullard reissue in those. I don't know what other tubes are interchangeable with those. But I can already see how I might lose myself in a rabbit hole here. LOL

I'm scheduled to get the shipments in tomorrow. I'll let you know how it goes.

G

@gotog I also ordered some inexpensive (but reportedly tested and matched) NOS Sylvania 12AT7 from a reputable eBay seller that will be in mid. next week. The preamp has been running for about a week. 2 days ago I received the new 12AX7 Mullard reissues and burnt them in overnight. After about 24 hours I sat down to listen a bit. And knowing the tubes needed more time, I just put on some music that I was not so familiar with. I've been wanting to explore some Chet Baker. I put on a mid-50s release of the Chet Baker Sings album. Before I know it, the album was over and I had not thought about the system at all. I think that's a good sign.

At this point I'm completely down the rabbit hole. For better or for worse. But regardless of where I end up. If nothing got better from here, I'm really satisfied! 

I really appreciate all of the emails and advice.