What do you take when demoing new gear?

As a relative newbie and also someone who is planning on upgrading my setup soon, I was wondering what you bring with you when you are auditioning new gear.

I will definitely bring some familiar lp`s and cd `s, but do you recommend I also bring my own source components, like a streamer or turntable? Do you ever take your own amps or speakers? What about cables?

Do dealers even allow this?

Thanks for your input!