[Elecraft] KAT500 advice needed

[H A Layer]

Hooray--just received noticed of the KAT500-K ready to ship. (Order 
dated May 18). This will be my first experience with an ATU, so I would 
appreciate advice.

My rig consists of the FLEX-3000 transceiver and a KPA500 linear.  I 
only operate SSB or AM. The T/R is a simple rotary 2P3T switch connected 
to both PTT lines
that allows three operating modes: Pos 1: Receive Only, Pos 2: Transmit 
with Flex only, Pos 3: Transmit with Flex and KPA500. Since the switch 
is rotary,
when I return to receive, it turns off the KPA500 before switching the 
FLEX to receive.  I know this T/R is primitive, but I am paranoid about 
blowing up
the FLEX with any RF "residue" from the linear.  The delay is probably a 
solid half-second or more, so I sleep better at night!

I hope I can maintain this simple T/R setup with the addition of the 
KAT500.

Also, Elecraft asked me, "...Please note that we have released the 
Optional KAT500 to KPA500 Cable, E850463, for $24.95. Let me know if you 
would
like this added to your order. Your Kat500 will come with a KXUSB cable 
standard. If you would rather have the KXSER cable please let me know."

Are they offering two optional cables: E850463 and KXSER? I assume since 
I will not be using the K3, that the standard KXUSB cable is
all I need --but I am not sure.  Help!

73 Hal KK6HY