[R_burke]

I currently use KT88s in my Sonic Frontiers Power 2 and have an urge to listen to 6550s.  I've limited the choice to two that are readily available to me locally.

Sonic Frontieres Power 2
Philly Audio 7B
RAW Acoustics HT3s
REL Strata III
Shanling CD T-100

[Parnelli777]

I would give the re-issued Tung-Sol 6550 a try. I thought they sounded great in my Jolida 801.

http://thetubestore.com/tungsol6550.html

[woodsyi]

When I went from EH KT88 to reissue Tungsol 6550s on my Bella extreme Hurricanes, I detected a little more resolution along with a bit of brightness.  EH KT 88 had a little more bloom.  The difference, however, is much less then the difference I get from rolling the driver and input tubes.  I would really say that the difference from power tube  change is inconsequential since you will flavor your amp to your taste with the small tubes which generate much bigger difference in sound.