If you want to jump into NOS without spending a ton of money then old US tubes are the way to go. Don't get me wrong; the Euros sounds awesome but are priced high b/c of it. Go US and you should then be able to retube the whole phono section for $100-200. Roscoe is absolutely right, be sure to tell the dealer you'll be putting these into a phono stage. Low noise tubes may cost a bit more but should be worth it in the end. Buy matched pairs. IIRC, you'll need a pair of 12AX7s and a pair of 12AU7s. If there is one US 12AU7 I'd say to avoid it would be the RCA Cleartop 12AU7. Every single one I've owned has gone microphonic and there are lots of other people who've had the same experience.
And CHANGE OUT THOSE 6SN7S!!!! Rogue supplies the 99 with Chinese 6SN7s. They don't sound too bad but you can do so much better for not a lot of dough. Again, stick with US here, the Euros are just way too expensive and rare. US manufacturers made tons and tons of 6SN7s so you can find them anywhere for cheap. GEs and RCAs are nice and cheap and sound good. You can even get those on ebay if you're feeling adventurous/lucky. Be sure it's a seller with lots of good feedback and preferably one who uses an Amplitrex tester. Again, buy matched pairs but you can buy pairs from different manufacturers. BTW, in the 99 the 6SN7 tubes are oriented a little different than most manufacturers; you'll put one matched pair in the right two sockets and the other matched pair in the left two.
Have fun!
