shuguang makes pretty good 12ax7's and EL34's, but I'd never pay more than US$30 a pair
and I'll never buy non-rebranded/tested chinese power tubes again
they have a huge failure rate (20 to 30%), in my personal experience
the "good" thing is that they tend to fail in the first day, so if they last a week, they are not likely to be a problem after a month or two, like newer JJ's
so if you want a quad, buy a matched sextet, so you'll have spare matched tubes
on ebay you can buy unbranded shuguangs for $40 a matched quad
the top sellers by ruby, TAD and groove tubes are rebranded shuguangs
they sound better than the new reflektor tubes (sovteks, electro-harmonix, reissue mullards, new svetlanas), in my opinion, and better than JJ's as well
the svetlana winged C's sound slightly louder, deeper and more in your face, but a quad costs almost 4x the price of a shuguang equivalent quad
the shuguangs sound smoother, with a fuzzy midrange character
I can't compare them to an old original Mullard, though
my only experience with NOS tubes is with RFT and Tungsram preamp tubes