2 Quad EL34 sets for Dynaco ST-70


I am new to tube amp and I really need your help. I have one current quad Russian EL84 running in ST70. My friend gave me another brand new quad Mullard EL34 Russian tubes for me to test sound. What is the best way to remove old quad tubes out and replace new quad tubes? If I do not like new one, I also can put my old tubes back.
sanjose_audio_guy
Sag, which Klipsch are you using; I use the original Fortes and like them quite a lot. I have been thinking of moving up to Cornwalls? The LaScala's are not for me, but a pair of Altec Valencias may be in my future.
I currently use Klipschorn with Dynaco St70 and PAS 3. My friend has Altec Valencia which sound is good with mid-range. I used to have Cornwalls with sound is good but La Scala is much better with vocal for Jazz.
Nice rig there. The La Scala's just don't do it in the bass for me. I enjoy full orchestral music, rock and dance, as well as jazz and bluegrass so I need a kind of all around speaker.