6550 tube question

I posted this on AA, but as with most imporant (to me) questions, I like getting a "bifocal" view.

I'm going to buy a spare set of power tubes for my 120 Magnums.
I've been doing loads of research, and it seems this Svet 6550c is what I want, based on this criteria:
- We listen to mostly Cuban and Rock. This music combination requires a lot of speed and energy, but still a lot of smoothness and detail.

My understanding from the many excellent post I've read here, is that these tubes are just the ticked. They are powerful and fast, with no glaring weaknesses.

Please respond if I am right, wrong, or just plain silly.

KP

PS. system listed here:
http://cgi.audioasylum.com/systems/2709.html