Hey Brad,
I owned a Candela for about 5 or so years in my system, and rolled quite a few tubes over the years. I wrote this quick review to the new owner on some of the tubes I've had in the preamp:
Tubes are extremely subjective. A lot of it comes down to opinion, the quality of the tube gotten, your personal system and if it’s already warm, cold, bass heavy, etc. You can really balance out your system based on the tube you pick. What I’ve tried:
RCA Cleartop: great highs, and high end shimmer. I found them a little low and miss bass light. Didn’t have the punch I wanted. Just sounded unengaging to me. BORING.
Brimar: these are very similar to Mullards, except generally less expensive. Classic British tube! Great mids! Really punch where the cleartops don’t. But I think they’re missing the sub-sonic bass region. Top end is there, but they don’t extend as far as the RCAs. Perfect for rock music!
Amperex: My favorite tubes. They are very good all around. Probably the best for imaging. They have very good bass. May be lacking in mid details possibly? Very good for electronic music! I have a pair of 1960 USA Amperex's in my Dodd currently, with no plans to change.
CBS Hytrons: these guys are amazing! I had three pairs. BUT, I never had any that were in good condition. These are basically extinct, and if you can find a pair, I’d HIGHLY suggest it!
Telefunken: the most expensive tubes I had (in the Candela). Definitely one of the best. Possibly the most balanced of all the tubes. If they excel in anything I’d say micro detail, and a really balanced feel to them. They just do everything very well.
Maybe that's a little bit of a start for you! Again... YMMV, and my opinion may be the exact opposite of the next persons!
Also - I have no clue if they've changed the Candela over the years. If so, I believe it would be very minor updates. BUT I can nearly guarantee that the sound signature is almost identical.
Klaus said he doesn't suggest rolling tubes??... that doesn't sound like him

Yes, personally I always experience a little bit of tubes noise. I know some of it comes from the two radio stations close by... ones literally across the street from me, and ones a couple blocks away... Never would have thought to look for that when buying a house

Sucks when playing guitar too.. sometimes I can literally jam along to the radio through my amp..
