I have not heard the Super-7 and did not know much about it until a head-fi colleague and fellow resident of Copenhagen set me straight on its topology. (For example, I thought it was an OTL amp!).
So, what I have to say about the Super-7 is sheer guess-work.
But I do own the Stratus. I do have the AVVT meshplates, plus some older double plates and have tried other 2A3 tubes, as well. They all sounded differently. The biggest gap was between the RCA double plates (warm all over) and the AVVTs (neutral and balanced). The differences match my own mood swings when I listen to music. I also bought a large number of different types of 6BH7As. There are differences between them, but they are all warner then the stock 6N1P. I also have one early 70s 6N1P and some others from later dates. There is not that much difference between them and i am not sure that I am not imagining the differences. The stock tube is as good as any. The 6N1P has better detail and is more neutral than the 6BH7s and certainly a cleaner top end. It is also a bit grainy. On some days i think about temporarily subbing my Telefunken and Siemens E188CCs, but haven't done it due to electrical differences + Donald's warning. The Rectifier matters. My Raytheon 5U4GB outperform the stock Russian tubes on the bottom and top ends, particularly the bottom. Nevertheless, the stock Russian 5U4G is no slouch. I use it a lot because my supply of Raytheons is not that large.
What i like about the idea of the Super 7 is the 6SN7 driver and output tubes. I would think that the brand/type/vintage of the 6SN7 driver (or electrical equivalent) would have a large impact on what one hears. I have a lot of vintage (i hesitate to call them NOS) 6SN7GT "type" tubes and found, for example, that driver selection made a large difference in what I heard coming out of my SinglePower MPX3 Slam SE. But so did the output tubes. I don't know if this will be true of the Super7. What I do know is that all of the GT-types (including the 6SN7W and WGT) are getting quite expensive, while the term NOS is being heavily abused. There's a lot of uncertainty, here. But with claimed NOS pairs of, say, Raytheon 6SN7GT/VT-231 T plates going for over $250/pair compared to $50 for a pair of used tubes (usually flat plates), there's a lot of room for randomness to set in. In my MPX3, the sound differed dramatically depending on the tubes I used and where I used them. The same is true for the effect of the 6SN7GT driver on my preamp and a Class A KT-88 triode wired PP amp I have where both the driver and phase splitters are 6SN7GTs (although the KT88/6550 tends to dominate).
With the Stratus, the differences are just not as great as I experienced in the MPX3. Thus, there us less uncertainty about what you will hear and what it will cost to tube to this amp. Yes, a Shuguang 2A3 tube will not sound as good as an AVVT or an EML. But the AVVT is unobtainable and the EMLs are in the $500 range (i have their 45 solid plate, not their 2A3). Go over to the Stratus thread. Despite minor disagreements, pretty much everyone describes the same sound.