How upgrade/modify-able should it be?
---major parts upgrades, circuit upgrades, component flavour

What is the price-point?
---no sense laying out an 845 amp for an EL84 crowd

Parts availbility?
---new production parts, or shall we do some hunting for vintage stuff?

I personally don't like the idea of needing new Iron to take a design to the next level. Aside from initial cost, there don't seem to be any real down sides to going after the good stuff.

Excluding vintage stuff seems like a reasonable idea, good new production for all but some of the valves is pretty easy to specify.

Where would *YOU* start?

regards,
Dogulas