Would you mind linking me to the exact tubes your talking about that pair well with the he-500?
What about these?
I can't find much on AMC.
The Good Points (from the listing)
They are 6922 valves. A higher Quality.
They cost $52 a pair.
Couple things I don't like.
The listing says CCa. Unless these are German made. Siemans. The they ain't CCa
It looks like the seller put every conceivable tube designation in the listing.
They are from the 1980's I think you can find some late 60's for $65 - $70 Bugle Boy's or Orange Globes come to mind.
Again, I haven't heard he-500's so I can't give you an opinion.