For longevity and sound quality, I would suggest General Electric 5670 5-Star at a 'reasonable' cost. I don't know what they cost nowadays as I bought a small stock some 5 years ago. They were manufactured to exacting specifications and should last many 1000's of hours. I've used them in a MJOLNIR 2 for some years with no problems.Ok, I just got some adaptors from Garage 1217 which are way nicer than anything you can get on ebay and not much more expensive, so I'm gonna try them.
So aside from the WE396As, which would legit cost more than I paid for the amp and I am just not going to do that. What are some relatively inexpensive 5670s I can try? The Philips JAN 6922s I'm using right now do sound pretty decent though, definitely a good improvement over the stock ones for me at least.
NOTE: These do need adapters