[Amps] Alpha 8410 using 4CX1500B - why?

[Peter Sils via Amps]

I recently acquired a slightly used 8410 (mfg 3/2014). I was surprised to learn it had 4CX1500B tubes rather than the 4CX1000A's.

Looking at the RF Concepts website for tubes I notice the price is lower on the 4CX1000A ($475) than the 4CX1500B ($525). 

>From what I have gathered the drive requirement is higher and the output is lower.

Can anyone shed light on why Alpha chose to go with the 4CX1500B's?


TNX in advance of your insights!

73 Peter
KD0AA