sonofa_lembic, it's great that you've found your perfect rig!
However, I have to comment on the amp thing.
First, I doubt that your Carvin or Samson put out anything like thousands of watts. Carvin, in particular, has always had incredibly optimistic specs, rating an amp that is in the 2-300 watt per channel area as thousands of watts by rating it at peak power at 1khz at a pretty high distortion level. Almost any amp can put out thousands of watts measured like that. To truly put out thousands of real watts (i.e., at full bandwidth and low distortion for longer than a few hundredths of a second) takes more current than you get out of a standard circuit. The Carvin, which seems like a very nice amp, claims THD< 0.03% @ 50% output, which means that it's really a 350wpc amp at 8 ohm. Not terribly shabby, but not quite what the marketing claims. I have a power amp (A QSC that is designed for stadium installs) that really does put out 800 wpc at 8ohms continuously at full bandwidth and low distortion that bridged to mono will do 2200 watts at 8 ohms at full bandwidth and low THD. I bridged it for one gig and it literally caught the speaker on fire, with smoke billowing out. Thousands of watts is simply not an option for a bass rig without blowing it up. Even the GD wall of sound was 4 Mac 2300s for the bass, so 1200 watts, which weren't run flat out.
I have an old McIntosh MC2105, my bass amp from high school, and brought it out to a gig a couple of years ago just for fun (it's really, really, really heavy, so it stays home) and is rated at 105wpc. It has nice meters on the front, so you can see how much of the power you're actually using, and it was really loud on stage, powering a Sunn double 15 JBL cab with one channel and a 12" JBL on the other (pickups run in stereo) and according to the metering, I was still pretty much in the 80-100 watt range. It was easily as loud as my Peavey amp that claimed to be thousands of watts, and it was coasting.
Second, class D vs. AB done right doesn't result in a difference in sound like you describe. In fact, class D is known for being lower distortion in general than class AB, at least until you hit clipping and most class D amps have built in limiting so you don't clip it. Early designs had problems, but many high end audiophile setups (and recording/mastering studios) are moving over to class D because of the improvement in the sound. The Hypex amps get great reviews. Over the years, I've gone, amp by amp, from a Crest CA9 (60lbs) and the above mentioned QSC, both AB, to a Crest Prolite 3.0, which is class D and weighs about 12lbs. It is not distorted or crunchy sounding in the least. There's no grind. I don't like grind (which is why I don't like SVTs). No good solid state amp which is not a purpose designed bass amp meant to sound like an Ampeg will give you crunch, grind, or other distortion.
If I had my way (i.e. roadies and a good road case for the Mac), I'd gig the McIntosh/JBL rig all the time, but the Crest/MAS (this speaker:
http://www.masoundworks.com/manage.numo?pid=6&module=shopping_cart&component=catalog&cid=4) combination sounds amazing. Utterly clean and very deep.
You're absolutely right on about the preamp!