Oas...as much of an engineer as I am, I did not predict how long it will take to wreck greenbacks solely through logic, I've seen it happen, plain and simple. And SPLs? were you assuming that despite the SPL rating the greenbacks are supposed to be for clean specifically over overdriven tone use? 97db peak is plenty loud AND you are pumping sounding through 4 speakers! If THAT isn't enough headroom, who are yoou playing for? Nine Inch Nails? Even Aaron North uses a single Marshal 1960 live AND he is playing arenas! You are one misled person, my friend. Despite the SPL rating, the speakers can take them because regardless of the peak decibel rating, you are distributing the overall load per cabbinet, over a range of speakers. However, the caveat is, they might not have as much "air" as other speakers which is why some people say over driven speakers sound best when they have a relatively low peak db rating. Engineering? Nah - common sense. Its analogous to stuffing a square peg in a circular hole.
Full throttle clean? Saturation = gain stages descriptive of channel 2 and 3 on the VH4, Herbert and the VH4s. Even with 2x50 in the power section on the VH4S, thats plenty clean. Just how loud are you playing to even notice saturation in a 100W amp? Here I can deduce 2 possibilities: A) your tubes might be bad or, B) your ears have awful tinnitis.
Oh yes - because you did say to call Diezel as a suggestion, I did, just to see if I was wrong about the SPL compatibility of the Diezel to Celestions, Black Widows.... The distributors, and Diezel, said the same thing that 97/ 98 is plenty loud, and unless you're playing through a 1x12, you shouldn't be able to wreck a 4x12 especially because of the tempered resistance rating of the speakers. Just in case you want to talk to them yourself, here are the contact numbers of the places I called:
- Salwender International in CA: 714 538 1285
- Moridaira in Japan: 0081 3 3864 1641
- Diezel GmBH in Dillingen 0049 89 930 67 27
You might be better off knowing how to speak Nihonggo to talk with someone at Moridaira and Deutsch for GmBH but, luckily, my Japanese is still great and I haven't lost my German in neglect. Diezel has a separate Service line that takes care of gear compatibility questitons and warranty services. I doubt I will ever need servicing for my amp but if it does, there are a lot of authorized shops where I live. Cheers!