Most tubephiles will agree that the 6SN7GT and VT-231 sound much better than everything else. At least initially I would just pick up a pair of Ken Rad VT-231 black-glass and a pair of Sylvania VT-231. The Sylvania VT-231 usually goes for about $40-50/pr used in good condition and $70-80 NOS on eBay. Ken Rad VT-231's usually go for about an additional $20/pr on top of the Sylvania prices. There are very few actual NOS tubes sold on eBay regardless of the claims. However I wouldn't let that stop you. You can a get a couple of used pairs cheaply on eBay and once you determine your preference you can buy the bigbuck NOS tubes from a more reputable tube dealer.
I have a Cortese so the Syrah maybe different. Anyhow, Mick told me that in the Cortese the rectifier is set to output 370 volts. The voltage-regulator tubes burn 70 volts and the 6SN7's use the other 300 volts. Keep in mind that the 6SN7 is dual-triode rated at up to 300 volts/triode, so 600 volts/tube. 6L6G's and 5881's can handle 250-300 volts with ease. Mick runs the tubes very conservatively.
As far as power tubes. I think the ST shaped 6L6G's (Sylvania, RCA, Ken Rad, Tung-Sol, etc) are better than the Tung-Sol 5881'S and they are certainly less expensive. With rectifier tubes, I prefer the GZ33 over the GZ34. The GZ33 is less expensive, probably lasts longer, outputs more current, and sags less than the GZ34. I have noticed a slight voltage sag from my Cortese with the GZ34. It only occurs on complex musical passages while I am playing very loudly.
If you have questions about what tubes will work in the Syrah as far as tube substitution goes, I would email Mick "the Man" Maloney. He'll be glad to answer your questions and I am sure his answers are more accurate than mine.