The 5998 with Amperex 6922s is the way to go...I LOVE mine with that combo. The only noisy tube experience for me was with a TS 5620, which is fairly rare...looks a lot like a 5998 with a 6AS7Gs guts. Great sounding tube, 5998-like, but very airy and open. It's a very high gain tube, and extremely microphonic, unfortunately. I couldn't even touch the volume knob without a "thunk" in my ear...
Anyway, I have yet to find any 6080 that doesn't suck, lol. They all sound dull and flat to me, completely devoid of detail, and lacking any sort of soundstage. Especially the 6080W* (A, B, or C) which is a military version that is reinforced internally to protect agains shock, vibration, etc. They make music sound like you are listening to it through a piece of plywood.
My favorite combos thus far (I'm still waiting on my Siemens CCa's to arrive from Deutchland) are:
5998/Amperex (US) 6922 (1959 PQ labels) - the best combination of detail, musicality, smooth top end, airiness, imaging, and detail. Magic. Great for live music, rock, blues.
5998/7DJ8 - very lively, warm, and lush sounding. Again, another great one for live stuff and acoustic performances.
5998/Mullard 6DJ8 - warm, sweet mids, smooth highs, very deep but forward sounding, like you are up close to the performance...seductive and realistic vocals, especially female voices.
7236/Siemens 6922 - bassy, "fast", detailed and spacious. Almost solid-state sounding...great for techno, electronic, rap and hip hop.
7236/Siemens 7308 - similar to the above combo, but a little more sterile. Extremely revealing and detailed, but almost to a fault (lol). Fantastic pinpoint imaging and almost 3D sounding. These are what I use when I want to go deep into the recording.
One other thing I'd like to point out...the BIGGEST and best improvement to date for me, beyond any tube rolling is replacing the stock output capacitors with Black Gates. It was an expensive upgrade...I sent it to Jack to do the work, and he charged me $200 for parts and labor, but it was well worth it. Mine are still breaking in, and they take a stupidly long tine to settle down, but my god...it's like a whole new amp. The soundstage is dramatically wider/deeper, the sense of space and amount of detail is just staggering. The stock caps are decent, but these really lifted the veil and removed what I considered a slightly congested sound. Do it...do it NOW! Lol...
I'm almost embarrased to point you guys towards this thread, but I started a tuberolling thread ages ago, when I was just starting out, but:
http://www.head-fi.org/forum/thread/375119/woo-3-adventures-in-tuberolling. Some of my observations back then were formed without much reference or experience, but I'm going to update it soon with all new details of tubes I've gotten since then. Here's a pic of MOST of my tubes:
