Do I have to brand match preamp and amp?

The only thing you have to match is the output impedence of the pre-amp with the input impedence of the power amp. The input impedence of the power amp needs to be at least ten times the output impedence of the pre-amp. The ratio can be higher, e.g. 11:1 or 15:1, but not lower e.g. 8-1, otherwise signal loss and noise may be present.

For example, a pre-amp with an output impedence of 1k ohms needs a pre-amp with an input impedence of at least 10k ohms

The only thing you have to match is the output impedence of the pre-amp with the input impedence of the power amp.

Since he is matching an Ayre preamp with an Ayre amp, I don't think there should be any impedance mismatch.

Another K-5xe MP preamp just posted today, at an even lower price.

https://www.audiogon.com/listings/lis8fb1d-ayre-acoustics-k-5xe-mp-excellent-condition-solid-state

Next thing you know there will be a thread titled "Why so many Ayre K-5xe MP preamps for sale?".

Of course. That’s what happens every single time I buy something 

That one was a steal, hence the reason why it is already sold...lol.

I have same issue all the time, just pulled the pin on a Lyngdorf and something else I had been wanting for a while pops up on eBay about 3 hours later....go figure.

Brand match for best and most coherent sound do this asap!!