[Elecraft] KPA-500 with 5w transmitter...

[Rick McClelland, AA5S]

I've been watching the details regarding the as-yet-to-be-released Elecraft
KPA-500 amplifier.   I presently own a QRP rig which puts out 5w but,
eventually, I'll upgrade to a 100w PA.  My question is whether the KPA-500
would function adequately with the QRP rig.  Presuming 15db power gain, I
would see about 150w output or 75w output with 12db gain.  Putting aside the
obvious question as to why someone would want to pair a $2k amplifier with a
$600 radio, does anyone see any reason why this wouldn't be advisable?
I've never owned any type of amplifier before so I am in the clueless
category when it comes to issues related to driving an amplifier.