Hi, I had the same questions about possible KT88 replacements for my orginal stock Valve Art KT88 and my tube guru gave me the following review to read about the current EH KT88's:
http://www.hometheaterhifi.com/volume_9_2/power-tube-comparison-6-2002.html
Additionally, he's a well respected SF Bay Area audio engineer who participated in a 2002 6550/KT88 Shoot Out that published in Vacuum Valley Tube publication. His private notes from the shoot out said the Gold Lions NOS ranked first (rare and expensive) while the EH's ranked second with the Tung Sols and JJ a discernable step behind. Consequently, I've decided to go with the EH's which are reasonably priced at $25/each at Tubedepot.com.
Also, on Ebay search "Amperex 6922", a seller has a batch of 1960's NOS for $35/each. Read the story and Feedback to evaluate his credibility. I ordered some. These are new, unused, discovered in a flood damage storage, without boxes and rubbed off lettering but test as new. Normally, these sell for $90-150. I thought it was a great opportunity and took advantage of it.
Good luck, it might be you won't do better than the EH unless you are looking for your tubes to address specific "sonic" needs.
http://www.hometheaterhifi.com/volume_9_2/power-tube-comparison-6-2002.html
Additionally, he's a well respected SF Bay Area audio engineer who participated in a 2002 6550/KT88 Shoot Out that published in Vacuum Valley Tube publication. His private notes from the shoot out said the Gold Lions NOS ranked first (rare and expensive) while the EH's ranked second with the Tung Sols and JJ a discernable step behind. Consequently, I've decided to go with the EH's which are reasonably priced at $25/each at Tubedepot.com.
Also, on Ebay search "Amperex 6922", a seller has a batch of 1960's NOS for $35/each. Read the story and Feedback to evaluate his credibility. I ordered some. These are new, unused, discovered in a flood damage storage, without boxes and rubbed off lettering but test as new. Normally, these sell for $90-150. I thought it was a great opportunity and took advantage of it.
Good luck, it might be you won't do better than the EH unless you are looking for your tubes to address specific "sonic" needs.