The old Ibanez Musician basses sound really good. Same with Yamaha BBs. My friend's dad used to have an old, neck through one in forest green. Very nice bass, was switchable active/passive.
If you like the Ampeg fridge but don't want to deal with something that big and heavy, there's the Berg NV610. Also some of the people on here are rocking Greenboy Dually cabs.
My 2000S 2x15 looks much heavier than it is, as it has neo speakers now. So while it looks like it must weigh a ton, it's actually pretty easy to move.
Some doom is mixed better than other doom. There's a trend of bass-less sludge bands right now, and it kinda works in studio, but so far most of them that I've heard don't sound that great live.
Old Electric Wizard I find the bass relatively easy to pick out on, but then, they were a trio at the time:
Dopethrone. Actually, listening to a
track from their last album, the bass is actually the loudest thing in the mix, even on crappy laptop speakers. As far as bass finding its own space... I actually find that in doom, a lot of TB's more cliche advice seems to work... namely, basically taking over the low mids. The uglier the solo tone, the better it will probably work in a dense mix like you have in doom. A lot of bass in doom is overdriven, so doesn't have as much difference in sustain with the guitars as you might expect (also true due to the volume).
Tube heads really shine when turned up (which, of course, they are in doom). Though lots of people use solid state heads, too, even sometimes for guitar.
Maybe get another 44-02 and put it in BEAD?