New tubes advice

Hi all

I have a Jadis Orchestra tube amp, she's a beaut! I've had it maybe 18 years now and replaced the tubes once. I'm considering replacing again now.

It has 4 x EL34 2 x ECC83.

What should I look for in a replacement set? I read they should be matched, or something? Any specific brands?

I'll have them fitted by someone else, as apparently as nice my amp is to listen to inside it's an electrical shock nightmare and I don't want to die while balancing it.

Thanks in advance for any advise!