I've had good luck with both Grant Fidelity and Parts Connexion, and also the Tube Store.
Several years ago I bought a matched pair of Psvane 6l6GC from one of those Asian sellers, these were to go into a guitar amp. They were so mismatched they were completely unusable. I contacted the seller and he explained they were matched for voltage but not current draw, WTF? He told me no problem, send them back for a complete refund, so I sent them back, he claims he never got them, no refund. From then on out I will only do business with reputable sellers.