If you DO add the K2/100 amp, for sure I would ALSO
add the "K2 Temperature-Compensated PLL Reference Upgrade":http://www.elecraft.com/manual/PLL%20upgrade%20rev%20C.pdf
It is simple and inexpensive, and Elecraft claims it"significantly improves the stability of the K2’s VFO, reducing drift per unit of
temperature by as much as 90%. It is especially useful with a K2/100, since
operation at higher power will cause faster heating inside the cabinet."
What hardware/firmware upgrades will I need to facilitate the additions?
Elecraft can give you the exact rundown, call them or drop them an email.
At the minimum, for the amp to work, you WILL need the latest I/O Controller Chip,
(on the RF Board). And the SSB Board chip version and Amp chip version
will need to be compatible. But if you are buying them both (Amp & SSB Board)
at the same time, it shouldn't be a problem. If you have or buy an unassembled
and/or older SSB board from somewhere, get the version number on the software first
and check with Elecraft.There is a boatload of mods out there for K2's of that vintage.
I would check them out at the Elecraft site. Some mods are "official"
and they even sell parts kits for them (i.e. the PLL Temp Control)
or the PSK-31 for SSB Board Upgrade. (Only for pre-2001 K2's).
I also had good luck going with the 14 matched crystals
for CW & SSB.
(Some go on the RF Board, some go on the SSB Board)
Other mods are described and "OK'd" by Elecraft, but they do not
sell the parts for them. (I.e. The preamp gain mod)
I am happy with my K2/100, but most of the time I use
the 10w plain K2 (w/ATU), as it is fun to operate when traveling.
BUT...having a SIMPLE 100 watt option is very nice.
GL ES 73, Ken AD6KA