I completely understand where ppl are coming from. Heck. ... I've got me a Aguilar TH500 - 4lbs of reliable ripper! !! And. ..as I've stated many times b4... I don't feel I'm losing that much (apart from weight) when I'm using it compared to the all tube amps I've got.
But. ... I just love the all tube tone. .. 95% of the time. ..all tube CLEAN tone and the whump that ONLY 6x6550 output tubes can give you.
I've used all tube amps all my life. I started playing on a Aus made (Bassman copy ) VASE Bassman 100 that my Dad bought me when I was about 13. It came with a matching 2x15" cab. Sounded great and I s'pose, influenced my take on MY bass tone forever.
I've NEVER liked ANY typical solid state amps. .. tried many many since 1975..... none had that bloom or solidity (to me. ...my opinion remember) that the all tube amps that I DID like, gave me. There ARE, of course, poor designed all tube amps that don't do it for me too.
It wasn't until the Mark Bass LMII came out that I liked ANY other type of amp. I felt the LMII had a nice warmth. ... since then I've like FAR more class D amps in these last 5 or so years than I've like ever before.
The V3 Rumbles are in that category. Imo... great sounding amps. I'd far rather a good, reliable,well designed totally tube free, class D amp than any other. .....except a well designed all tube amp like my favorite - the Super Bassman or an SVT-VR or the other all tube amp I've got - the Ampeg V4B reissue.
And. ...also as I've said b4..... I'd love a Rumble 500 head. ..but the cost of them here in Aus is ridiculous. ..so for the time being, I'm sticking with my Aggy TH500.
I've never really liked tube amps of any kind. One thing I like about the SVT is the punch, but I discovered early on that it was the cab doing that. I used a Peavey SS head into an original square-back SVT cab (my first real amp) and it was punchy as anything. The thing I never liked about full-on tube amps is the slowness - you call it bloom, I call it lazy response. I'm a very quick, funky/punchy player (in my head, similar to Rocco Prestia) and while I appreciate the meat of a tube amp, especially for a rock or blues band, I need the speed and punch of a solid state amp a lot more for funk. I also like to get my growl from a super-clean amp, not from distortion, which I find tube amps always bring. And then there's the compression... Oy. Lots of guys love it, I'm a very dynamic player and find compression limiting (pun intended).
Which brings us to the Rumble...
I find the Rumble to be a very fast-responding amp, but with a tube-like sonic meat

-)) quality. You say you like MarkBass LM II, and that stymies me - those amps are anything but tube-like; I have two of them, an LMIII 800 and an F500 and find them to be not only mid-heavy, but deficient in low end "torque," shall we say. This isn't to say the MB's don't sound good; they do, just rather the antithesis of a tube vibe. IMO.
You must have been doing backflips over the Genz Streamliner. Three-tube front end with Class D power. I had one of those too, and while I loved it in the store, I soon despised it. It had a dark and muddy tone I could never get to brighten up, no matter what cab I bought nor tried it with. Sold it, good riddance.
Then we come to Ampeg Class D, the PF line. I had an early model PF800. Sounded great for the hour or so that it worked before turning into a fuzzbox. Recently I tried a PF 500. Boy did that little amp bring the meat. Perfect Ampeg depth, the band loved it, and it was interchangeable with the SVT 4 owned by the band's guitarist. But I couldn't get past the thought of the PF 500 breaking down on me (some reports of that still happening with the PF500s), and my own recollection of the PF800 turning into a stone.
In the grand scheme of all that, the Rumble really measured up. Got a sound that's fast, punchy and clear, but with a tubey vibe and hard-as-nails reliability. The one thing it doesn't have is that Ampeg subsonic beef (boef to you chaps across the pond).
That low end push is the only thing I'm after at this point. I don't usually use pedals, but I just ordered a Tech21 VT DI, so we'll see what that brings to the Rumble.
Rock on, Garth.