I am a big fan of OHM’s. In fact I just refurbed a set of Walsh 5 LE’s using the latest 5.5000 drivers.
In reading through your post. A couple of thoughts. It sounds like you still have the same woofers as they just replaced the surrounds. With the same drivers you should get the “Same” amount of bass. However, if they changed the port tuning, you could get more or less bass, but with deeper extension now. It would depend on the port tuning. Otherwise, as the surround loosens up a bit your bass should improve a tad.
Second thought. If you are using the Jolida tube amp, it wouldn’t be my first thought with OHM’s. More than just about any speaker I’ve owned (and that is a lot of speakers). The OHM’s need power. So, I would give them a little gas for a while with a big old solid state amp (or Class D will be fine).
I do feel that the biggest difference between the original drivers in the Walsh 5LE’s and the new 5.5000’s is the midrange is much, much better. I also prefer the soft dome tweeter in the current speakers. I’ve had a few generations of OHM’s over the years. I’m not a fan of metal tweeters in general. If the midrange is more prominent after their tuning, then you might feel like you hear less bass also.
You could also just push them back 6 inches towards the wall. OHM’s really change their bass presentation based on location to the wall. I have some older Walsh 1’s also. It cracks me up how much bass they can generate when 6-8 inches off the rear wall and with a big old Adcom 5800 pushing them around.
If you don’t have a solid state. Run down to guitar center and pick up a crown amp and give it a whirl. They aren’t perfect, but they have a crap ton of power cheap and a liberal return policy.