Tube Rolling on a Symphones + audio experience

hey all..
I just picked up this most excellent preamp, and i'm looking to replace the stock tubes.
1 6x4
3 12ax7s

I just picked up a matched pair of GE NOS JAN 5751s for the output stage (replacing stock chinese 12ax7s), and im looking for suggestions on others to try here. I was leaning towards a pair of GT 12ax7 as they are supposed to be a mullard rebuild, and the previous owner suggested some good mullards.

I'm looking to add some texture, some fowardness perhaps in the presentation. some midrange enhancement would be great. current bass responce is powerful, so i'm not looking to fatten that up.
stock, its sweet. but I want it dripping sweet.

amplification is provided via custom ICEpower modules, which is pretty neutral sounding to me, and plenty lively.

awaiting your comments.
got some to sell? hit me up!
I have the same pre-amp in my bedroom system and just love it! I prefer Telefunkens to anything else they last seemingly forever and have a very neutral/correct signature. Try the re-issue Mullard Groove Tubes (about $20) each , which should give a warm sound, if you prefer that. Another to try at reasonable cost would be Mazda (French, not Japanese car) chrome plated 12AX 7's from the 1950's/early 60's, as some folks literally rave about them also (I have yet to try them). You'll need to have some 6X4 rectifier tubes on hand, too (I use RCA's as they are readily available and of good quality). You are going to have lots of fun with this. By the way, there are lots of fakes out there, so be careful, especially when spending lots of money. East German Telefunkens look just like the real thing and are absolute junk. When buying telefunkens I prefer the used one's labeled DYNACO or FISHER as they are the real ones, and, since they are used, they are typically cheaper too. Happy Listening, you made a great buy!
Nick, I use the Concerto plus phono and it has the same tube configuration. My favorites are early 60s Amperex white label 12ax7 then the Amperex orange globes are also pretty good with just a tad bit less warmth, next are the new Tube groove mullards 12ax7 which really surprised me as they have killer bottom end with just a slight rolled off top but still a good tube. I also have tried triple mica 5751 but were not good sounding compared to my favorites. I have also tried mixing 5751 and 12ax7 but that was one of the least enjoyed configurations. Another good tube are the branded Baldwin organ tubes which are my third favorite ones. I talked to Nelson and about the 5751 and he agreed the 12ax7 were better sounding and he also suggested not to mix them. Consider swapping out the newer 6x4 to somethng like the made in france Radio Latique as they are cheap to roll and sound great.
get some tungsol tubes i had the gt 12axy in mine a tong sol 12ax7 in middle socket and a tungsol retifier tube and it was sweet,i did alot of tube rolling in that preamp,rca tubes were nice to play with the rectifier tube,also run some silver interconnects to will get really nice,also if your good with a soldering iron you can modd the power supply on that ,by changong some caps and it will blow you away.i got my info on mod on the net somewhere.i dampened the chassi with some vinal floor pieces and left the top cover off it needs dampining bad,good luck
i'm very good w/the soldering iron. i've wanted to do some upgrades, but dont know where or what. I'm confident I could replace anything on that board, its just knowing what to replace that kills me.

thanks for all the suggestions folks.
getting some GT 12ax7 mullard re-issues was on my "to do" list.