I looked into the Darkglass amp at one point and it looked like they were using a 1200 watt power section. I can only guess they rated it for 900 so no one would ever be able to accuse them of over rating their amp. Yes, that thing is stupid powerful.
I had the Rumble 500 at one point but returned it and got the Rumble 800 head and 115 cabinet. I have zero practical application for all that power. I just have this dream of eventually combining the 115 with a 210. Which was pretty impractical since I could have just kept the Rumble 500 and added the 115 cabinet for a few hundred less than what I ended up paying. Mostly I just wanted what I wanted, because I thought it was cool. I forgot where I was going with this. I’m just nerding out about amps.
Yes, the Rumble 500 is great. When it comes to how much you get for your money, the Rumble line is hard to beat.
I’m not trying to sell you on the Rumble. I’m on a budget, so that’s where my mind goes. The Rocket Bass line are a little more expensive but also pretty great. It’s worth doing a comparison at a guitar store and seeing what appeals to you.
Both the Ampeg and the Fender have their own sound. The other side is to look at something that’s very clean. The BAM is pretty good example of this, but I found them to be too clean and benefit from using a preamp pedal. There is nothing wrong with using a clean sounding amp. For a lot of people it’s exactly what they want. If you’ve seen any pedal board posts from @John_E , his set up is all about using a clean amp and front ending it with a selection of different preamp pedals.
On the other hand, any amp with an effects loop will let you skip the built in preamp so you’re getting just the sound from your preamp pedal going through the power amp of the amplifier. this gives you options of using the baked in sound of the amp, the sound of your preamp pedal without the baked in sound of the amp, or stacking the two. Stacking is what I do. I use a Tone Hammer into the front of the Rumble head, combining the baked in sounds from both is very satisfying to me. @PamPurrs worked with her setup and found she liked using the VT Bass DI preamp pedal better by itself and skipped the Fender sound altogether by going through the effects loop in.
Finally, if you do want an inexpensive head, and plan to skip the built in preamp, the Harley Benton bass heads use the exact same Class D power section used by virtually every bass amp manufacturer in the industry (Fender, Ampeg, TC Electronic, Mesa Boogie, etc.). @DaveT has one (maybe two?) if your curious about them.
I know this is long but since you’re delving into the amp rabbit hole, I figured I would try to illustrate how all the options fit together.
If you made it this far, thanks for nerding out with me!
And, if you have any more questions, there are plenty of folks here to help with whatever setup you have in mind.