I have a LOT of experience with this subject, I even purchased 2 different VH-4's because the debate drove me absolutely insane, I had no intention of keeping both, I just wanted to have a "newer" one and an "older" one side by side to A/B. I've owned a 2004, a 2006, and 2 different 2007 models.... rather than go into some huge debate, I will tell you that they all sounded completely incredible.
Yes, the "newer" ones have more gain, but when people say this, they are talking about STUPID amounts of gain, this doesn't mean the older ones don't have enough, I never ran the gain on my older ones past 12 o'clock and it was MORE than enough, and I play a lot of heavy styles of music.
You absolutely cannot go wrong with any of them, I can't speak for the much older models, but the models years I mentioned were all extremely close in sound, the older ones are a bit less compressed and "fizzy" I would say, but that's about it, more then enough gain on ALL models, functionally they are all exactly the same.
Just make sure whatever year you get to throw 6550's in it, I know papa may get mad at me for suggesting this, but they are incredible in the amp.
Here is a comparison video of EL-34's and 6550's, and also another video of me just jamming out, please keep in mind the head in the videos is a 2006, I am on channel 3, and the gain is at noon, so that gives you an idea of the amount of gain on the "older" models, it's MORE then enough, hope this helped!!!
Make sure to watch all the videos in HD, it really helps the sound, in the last two videos I just play the same song for comparison purposes, you can't tell much in the video, but the 6550's make a HUGE difference, whether or not the different is what you prefer is subjective.
If you watch just one video, watch the first one, it is the quintessential Diezel VH-4 channel 3 tone IMO, and it's not a "newer" one.
This was taken to test my iPhone speaker input, gain is at noon, head is loaded with 6550's:
EL-34's
6550's
A wonderfull amp!
