6550 to KT88

I have a rogue audio zues that came with the EH6550's. I was expecting the EHKT88. I was wondering if there is a big difference in sound staging and bass by going to the KT88, also which KT88 is the most well rounded? Has anyone tried the SED pearl cryo valve svkt88. The info I have read is that they are best modern production KT88. Kind of pricey for a new tube,$145.00 a pair. I have read good things about the jj KT88 and the winged 'c' KT88 from the original svetlana plant in russia. I have been thinking about trying the kt88 or KT90, but it sounds like the kt90 is going in the wrong direction. Are the electro harmonix kt88s better than the 6550s?

Be very very careful with the JJ KT88s. Their reliability was a disaster for me with them not lasting more than 6 or so months. Upon destruction, they launched a power resistor in the amp (ARC VT130) each time. I went back to 6550s, lost a little of the midrange warmth but gained a more neutral tonal balance and reliability to boot.
John

Thanks for the warning . I was considering the JJ's.

Jaq , Your concern over JJ is realistic but a maddening tradeoff because they do have the best tonal qualities of any current KT88.Both JJs I bought from a well known Canadian tube dealer went bad frying 2 different ASL amps--- expensive repairs both times.The word from a previous thread about this stated that KT88s are the most easily damaged tubes and do poorly in shipping. Try finding a vintage amp that uses 7591 power tubes. This is great tube sound.

Hi,
I rolled the svetlana 6550 and ei's kt90 on a pair of jadis Ja-30 before i changed to the Jadis se300b's.
I loved the 6550 over the kt90 although the lost of punch on the bass region. The mids and highs never sounded more sweet and relaxed. Since I´m using 93db on the low octaves the less power on bass wasn´t an issue. The great "BUT 2 here is that mids are made with a vintage jbl driver and horn and are very sensitive to "Harshness". I think in a regular dome midrange-high driver the kt90 maybe the best way to go.