The DOD is a bandpass filter, isn't it? If you just want massive dark bass, you're going to want to stick to a lowpass filter. The Moog certainly does get a lot love, but pretty much any LPF with the sensitivity rolled ALL the way off will do the job. You also might want to consider a bass boost, like the EHX Mole, Devi Ever Dark Boost, or something like that. Maybe even the DOD Meat Box (?)
Love the Meat Box for what it does but I wouldn't use it for dub. Then again I've been too afraid of speaker damage to ever use that thing except to goof around with my practice amp at home at low volumes.
The FX25 is a BP filter I believe, but it's sweep is HUGE and with the sensitivity rolled off it works perfectly for insta-dub tones. The only issue being that you have to like the sound as is because you have no means to tweak it. The Moog (and Xerograph and Brain Freeze/Photron Filter) all give you more control. You can set the cutoff point (especially useful for a static LPF), adjust the resonance and even add some clean blend if you desire.
Again, my recommendation (based on size, features, the tone from clips, true bypass, and of course price) is to try out the Iron Ether Xerograph.
My board from my ambient dub band had both the FX25 (in a blend loop) and the Moog