Can connecting 2 XLR cables together degrade sound

Don't plug the two together, bad idea. Sell the shorter ones and get the length you need, even if you have to go to a less expensive brand of cable.

Ozzy

You might find it cheaper to sell your existing cables and purchase a used 2 meter pair.

Also to answer your question ,in my opinion, yes. One must consider the fact you are not only increasing the number of solder joints between your amp and pre amp and the connection itself will not have the same properties as a solid wire.

Damon

In my opinion the more connections there are the greater the likelihood of minor sound change. It might not be noticable, only you can tell if the difference bothers you.