I'm in TOTAL agreement here. I used greenbacks for a bit, but man I didn't like them at all. At lower volumes, they were great, but as the volume got higher and higher, it really made my tone change for the worse in my eyes. For lower gain amps like old Fenders and Marshalls, they are great. But for higher gain stuff, you don't need speaker breakup in my mind either. I've been really digging the CL80 and K100 lately as they have the same tone at lower volumes and higher volumes. The CL80 right now has been my speaker of choice, as its very warm, yet very punchy, and has great chime on the high end. But, it sounds consistent at all volumes.
I also agree that speaker breakup, to my ears, doesn't sound THAT desirable.
It's such a delicate balance with speakers. You don't want to get one UNDER-powered. You want to get that cone moving and pushing some air, but you don't want it to distort either.
I totally agree here man. I'm totally with you. I get all my tone from the preamp, and let the power amp make it louder. It's why I've never liked EL34's or 6L6's as much as 6550s. The louder you get, the harsher 34s or 6L6s got for me. Since the headroom on 6550s is high, it gives you the same tone at lower volumes and higher volumes. And they have sweet, warm midrange!
I go after more vintage tones.. and power amps tones.... preamps are much fun... but the real juice for me is a mildly driven power tube tone.
I am going to have to do some more study on speaker breakup- .. most people I talk to refer to it (not in the fart levels) as a good thing.... and one of the essential parts of the full distortion sound... and I am quite sure I heard some recordings/ comparisons a bit ago in smaller combos and heads that were attributed to it.... guess i learn new stuff everyday!