The big Harbeth's do better with neutral tubes IME. Can't speak for the 12AU7's, but I always found NOS Mullard CV 4004's to be a nice neutral tube.
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Amperex, Telefunkens, Siemens tend to work very well, IMHO. If you wish to stay away from warm, best to avoid the British tubes, Mullard, Brimar, etc.
Right now I am rolling a pair of Pope 12AX7's (fancy Amperex Bugle Boys) in the phono stage, V01 and V02. A Telefunken smooth plate 12AU7 in the V03 line stage with a Mazda Silver plate 12AX7 in the V04 line stage.
Driver tubes V05,6,7 are RCA Cleartops. Power tubes, V08-V11 are Psvane KT88's. Works well for me, as always, YMMV.
On the power tubes side, I had a VAC Avatar Super and rolled a lot of KT88 and honed in on the gold lion reissues as having great overall presentation. I also like the ruby tubes as well. If you like a ton of detail the EH did that better at expense of midrange and bass. Good luck and let us know how you do.
I am very pleased so far with the RCA cleartops in the driver tubes and the Telefunken in the V03 linestage.......I ordered some amperex bugle boys for the phono and a mullard cv4004 to try in the V04 linestage.....
I would say the upgrades so far has many the sound smoother and punchier........the stock tubes were less refined................
You might also try as driver tubes three Philips E80CC tubes made in Heerlen. These are 12au7 subs with a higher filament current requirement which works fine in the 160iSE amp, but only in the driver section and importantly not in the preamp section on the left. I have used them for a couple of years now and like them a lot. These Philips Heerlen E80CC tubes are identified by a delta symbol in the 4 or 5 digit tube serial number marked on the glass near the base. Philips E80CC Heerlen tubes were also marketed under the Valvo, Telefunken and Siemens names, but so long as they have the delta in the serial number they were made in the Philips Heerlen plant which is where they were apparently made best. They produce a more powerful, clarified, detailed presentation with the sound perhaps a bit more forward than you would get with standard 12au7s. I like them better and use only these in the driver section. Please do not use one of these E80CC tubes in the left hand side preamp section. A pinched glass version of these tubes can run a lot of money - hundred of dollars each, but I use just the normal versions which can run you about $50 apiece on EBay. I use 2 or 3 of Herbie's HALO-III tube dampers on each tube which may be similar to the the pinched glass effect.