Is system synergy worth having matched components?

If you ask a dealer, they will tell you it is very important to use the same brand pre and amplifier,as it is the easy way to go and they can increase the sales.

In fact, if you are a experience guy, you do not need follow that  way, you might choose your way, and better one

If  you are new, do the pair with same brand.

Most very good match is not going to public, it is in some one's room. Hifi is  a exploring  journey, and that is most  interesting things inside itself.

No.

Most devices, like preamps, have an output impedance that is pretty low.
Most amps have a high input impedance.

if it sound good, then get more music and be happy.

@holmz : +1! Unlike gravity, synergy is an imaginary concept.

But am I doing myself a disservice by not even hearing the Odyssey Candela or Tempest preamp with the Khartago? 

No.

there are a LOT of members that mix and match equipment.

just as it was mentioned earlier, if it sounds good, then leave it , enjoy it and buy music to listen to.