Yes a tube tester is on my short list of "important" items needed. Honestly that level of commitment was what I feared originally about tube equipment but despite myself I'm overcoming my xenophobia. The quality of musical reproduction is so "human" that I'm getting braver and beginning to embrace the cool details of tube design and magical sound quality. I'm so techno-phobic that tubes seemed unnecessarily demanding. But, contrary to my stubborn comfort zone addiction, I've begun to embrace the additional knowledge set that tubes require. "Old dogs new tricks" adage rings true for me except gaining amazing music quality beyond anything I've ever thought I could own has lead me down a path which contained delights worth the uncomfortable feeling of uncertainty. Yes, Chinese NOS which, I'm reliably informed, far out performs current production models. Not cheap though at $400 per quad for Raven Heads through Raven Dave of Raven Audio but my ears have never experienced such a treat!!