replacement tubes for Cayin A50T

I am fairly new to tube amps but really enjoy my A50T. I listen to mostly jazz, blues and classical. My speakers are KEF-104AB. While I really enjoy A50T I am hoping for deeper sound stage like my brief encounter with a McIntosh MX110 + MC240. On the A50T good recordings are warm and present pin point placement of instruments and voices and a wide stage but the depth of the stage is behind the speakers. If my memory is correct the McIntosh soundstage was both in front and behind the speakers. I have read varied opinions about different EL34/KT77 choices and have also read the preamp tubes affect the sound stage. The A50T uses 12AX7EH and 12AU7EH. Do you recommend I start with the EL34s, 12AX7 or 12AU7?

Within the EL34 choices I have read more praises for Winged "C" SED then any other. I have also read Tung-Sol sounds the same but a bit cheaper. The final noteworthy choice is the Gold Lion KT77.
I use to have the Cayin TA 30 and it used the same tube complement your amp. I found that the 12ax7 position had a great effect on the sound. I always liked to replace that tube in other amps with the GE black plate 5751 but found that I lost low volume dynamics when I tried that with this amp. So I tried a pair of reissued Tunsol 12ax7 and they really did the trick for me. I think the increase in gain of this tube over the 5751 really helped. Then I tried about every combination of power tube possible and finally settled on the JJ kt77. Just a very balanced sounding tube to me. Much better bass than the el34 and to me better midrange bloom than the kt88/6550 type tube. I ended up with the amprex bugle boys in the 12au7 spot. Very nice tube that seemed to broaden the soundstage considerably
The 5751 is such a great stager that I can't help but say try the RCA late 50s vintage triple mica blackplates white letters or if you can the Sylvania triple mica blackplate is very detailed and tops in terms of demand. The GE tends to have a slighly overwhelming bass response which may have obscured the low level details and dynamics.
The other suggestions I would venture is the EH6CA7 fat bottle for outputs. As a rule I used JJ E34L exclusively until I heard this incredibly dynamic Russian tube. I am not convinced it will respond to every amp however so caveat emptor. I am in a wait and see position, on the Gold Lion reissue KT-77s but the KT-88s are all what they promised and then some.
If you can swing it try some 7316s in the 12AU7 position. They were made by Amperex Heerlen Holland and typically OEM labeled for early 60s computing and testing devices by Beckman and Hewlitt Packard etc. Make sure it has an acid etch with Ct, a number, (1-5 are early and desirable) then the Heerlen right triangle, with __two other numbers on a line below. These tubes can be outright halographic. Yes they are expensive but supposedly very long lived. There are always a couple of pairs on e-pray every week. I rarely had trouble if the seller gives you the etching info.
Larryrx7 and Mechans, thank you both for your input. You both pointed to the 12AX7 and 12AU7 which supports my suspicion that the soundstage starts there. Larryrx7, I do have the Tungsol 12AX7 installed and agree the amp is more open compared to the stock 12AX7 in the A50T. Now to research an Amprex in the 12au7. At first glance at ebay they won't be cheap.

Thanks again,

Try an RCA cleartop in the 12au7 slot. They are cheap and sound great.