GEC KT88 single-getter vs. triple-getter tubes


I recently received a Unison Research Sinfonia integrated amplifier and tried various tubes with it. As output tubes, I tried three-getter GEC KT-88 tubes which are great but I felt that they are overblown and rather fat sounding and lack air and HF extension. The stock tubes (Sovtek KT-88 marked "Unison Research") and somewhat lighter and brighter in a good sense and I thought I would keep them as output tubes, until I inserted the earlier vintage single-getter Genalex KT-88 tubes, which have more high frequency extension and transparency and don't have such excessive "bloom" I was suffering from. Has anyone had similar experience with these two varieties of GEC tubes? I will also appreciate any tips about a reliable source of NOS/NIB GEC/Genalex KT-88 tubes.
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I compared new GL KT-88 with 1977/78 vintage British-made GEC KT-88. They are not the same. Here are my comments:

I played the new Gold Lions for approx. 20 hours (perhaps its not sufficient). My first impression was that they sounded very similar, but it is not so. They are similar in terms of power - they have a very dynamic and powerful sound, with overblown midrange and truncated highs. The original GEC tubes have more air and midrange delicacy - yes, it's delicacy which the new GL tubes lack. Besides, the new tubes have a characteristic Sovtek-style metallic sheen in the midrange, which is not present in the original tubes.

The amp is Cary SLI-80.
I personally found the reissue GL to be fantastic in my Jadis DA-60. The Chinese tubes I had in another amp were thin and lacked definition simply no comparison. I am an unabashed fan of the Reissue and highly recommend it. BTW the input and driver tubes in the Jadis are rolled without any diminution of the KT-88s quality.
Im my other amp (Hans Audio KT88), the reissue GL sound fantastic - clear, lively, dynamic and powerful.
After many more 6550 and KT 88's tried and tested I have to go back to my recommendation for the Shuguang made GEKT-88's not the same as the KT88-98 not to be confused.
Also the newer Treasure line of Shuguang made tubes are fantastic.
I still keep a stash of (NOS circa 1960's)Tung-Sol 6550 as in triode strap mode sound the very best I've heard in delicacy, defnition, timbre, tone and balance. period!! then if you wish for more bass the Ei made KT90's are it for sure though it sounds slightly harder than the NOS Tung-Sol (I'm nitpicking here)the bass in terms of shee grip slam and definition is 2nd to none, so, again fun to roll between these 3.
I have not heard the Golden Lions is such a long time I could not possibly speak intelligently about them, here is my short list.
I was not lucky enough to be exposed to a $2,000 quad of Genelex KT88 so can't mention them either, but just about heard everything else in my system, Including some GE 6550's and other Tung-Sol made versions (Sylvania branded and RCA branded).
6550 is a must listen for some music fans since it might interact better than KT-88's in some circuit designs and with some other tube drivers in the circuit.

I also heard some of the newly made russian and Chinese 6550's my my heart was not won over them, I would consider more suitable for like a Hammond Organ tube amplifier or something of the likes maybe lesser resolution system.
My system nowadays will pick on every little detail and throw it in your face due to silver cabling througout and high efficiency speaker drivers, extremely transparent and musical if the chain is very good

Chinese amps to recommend, Yaqin, Music Angel, Cayin, Shanling
For Cheap of course by no means any of the manufactured Chinese stuff will improve upon the quality fo US manufacturers such as Quicksilver Audio, Audio Research, and a few others.