But most of the systems have serious issues with bass lag. Especially tubed ones. Wobbly, undefined, out of rhythm bass.
I find that if one is careful about the match between the amp and speaker that this need not be the case at all.
In fact I've found that tube amps often deliver more natural bass than solid state.
Now my speakers are 16 ohms, as that better takes advantage of the capabilities of any tube amp which is how you want to approach it. My speakers also go down flat to 20Hz owing to dual 15" TAD woofers. Plenty of impact, extension (my tube amps are full power to 2Hz, so no measurable squarewave tilt at 20Hz), no 'wobble' (whatever that is) and plenty of definition.
Many speakers today are 4 ohms in the bass and otherwise 8 ohms in the mids and highs. An example is the B&W 802. This is not a tube-friendly speaker and designs like this should be avoided if you want to get the performance out of your tube amps! If you use the 4 ohm tap, the output transformer is less efficient and may lose an octave off the bass response. Why do that when tube amplifier power is more expensive?? Instead (and this is true of any amp, tube, solid state or class D), don't make the amp work hard for a living. Its life should be easy like a walk in the park. Then it makes less distortion and will sound more like real music.