Better tubes than factory installed tubes on the Rogue Audio Perseus Magnum Preamplifier

lowrider57,
First of all, thank you on suggestions.
Yes, Odyssey is SS Amplifier and I replaced Focal 807W
with towers 836W. Very revealing speakers.
They don't go deep but the bass is good for the
size of my room (13" x 18").
I can get Telefunken tubes from Europe for 60 Euros each.
Should I replace all 4 tubes or just the front tubes.
Thanks