You could test the tubes, but I would also be inclined to re-tube if only for the peace-of-mind effect. Definitely talk to the manufacturer to get their take on what works best with their products based on actual experience. Be very careful to find matched tubes with the correct combined values for each channel. Doing the NOS thing can be iffy and expensive -- there are some really good new tubes available today. Good luck.
Please help a new tube user!
I'm anticipating my new used Jolida 502b integrated amp in the next couple days. The seller didn't know how old the tubes on it were (3rd party seller) so should I just assume they're old and buy a new set? Also, what tools besides a voltmeter should I have for my tube equipment. Thanks! D