Every application is a bit unique, so the results will likely be also, but I used the Yugoslavian made Nationals in my Lazarus preamp for a long time. Once those needed to be replaced I put in some JJ ECC803s, which I liked enough to use for a year or so, but never felt they had the same magic mids of the Nats. I've since gone with the new issue Mullard CV4004 and have found those to be sweet and clear.