@haimra The Vivid Kaya 45 appears to be a poor match for tube amplifiers. Its impedance is a low 2.8 ohms at about 130Hz; from the Stereophile measurements its clear that this speaker is designed for an amplifier that can behave as a voltage source. A good number of tube amps can do that, but no tube amp is going to strut its stuff into a low impedance where power is demanded.
Further complicating matters is the low efficiency of this speaker, which is meant for solid state power which is inexpensive. Quality tube power isn't cheap! When you correct for impedance this speaker has an efficiency of only about 85 dB. That means in most rooms with a tube amp you'll be wanting 400 watts to prevent clipping of the amp at lifelike levels.
Seriously, and this is coming from an amplifier designer, if you want to really see what tubes can do, consider replacing the speakers first. When looking for a speaker, pay attention to how the woofer or woofer array is set up. You want something that is nominally 8 ohms in the bass region, usually meaning that only a single woofer is employed. You may encounter some speakers that have dual woofers (wired in series) where the impedance is high- like 10-16 ohms instead of 8; such speakers are rare but they will work great with tubes. Avoid any speaker that is 4 ohms or less in the bass (which is what you have).
Sorry to be the bearer of bad news but if you invest in some of the higher powered examples suggested earlier in this thread, you won't get the performance out of those amps that their prices suggest!
