Siemen tubes in Sonic Frontier line 2 ?

I have a SF line 2 and I am considering replacing tubes with Siemen tubes. How will this effect sound? Any other NOS tubes to recommend? George2
I went with Siemens NOS in their phono stage--incredible upgrade. Siemens worked very well. I tried Mullards--and they worked like an antenna, picking up a lot of noise. I spoke with techs at SF and they said that the Mullards are a known problem with their gear.
The Siemens E88CC are one of the nicest tubes available for the SFIL2.You only need 2 to make a huge diffrence in the sound.I believe there is a matched pair at auction right here on Audiogon.The Sovteks in the line 2 are average.The Siemens will make the SFI sing.
I tried a pair of Seimens 7308s in the two rear positions of my Line 2 and did not like the big billowy, diffuse, forward sound stage they projected, and went back to the much more neutral-- but less euphonic, Sovteks. BTW, I also tried a set of Valvos, and also found them to be to euphonic for me-- guess I really like the neutral sound. To each his own, or "beauty is is in the ears of the beholder". But tube rolling is fun, and not too expensive, so give it a try. Happy Rolling. Craig.