I play bass about as much as I do guitar and went through the journey of looking for a new bass rig about a year ago.
Right now class D is the thing in the bass amp world. They're small, light weight like (less than 10 lbs.), plenty powerful, and pack a lot of punch. At the top of the pack are the Mesa Subway series and Darkglass amps.
They're both completely different animals so which one would be best would depend on the application.
Mesa Subway series is top notch and can cover both modern and classic bass sounds. They're more or less the successor to the older carbine and walkabout series. The TT-800 is the flagship model and has 2 channels each with its own EQ; Subway & Boogie. Obviously the Subway channel is voiced similar to the other amps in that series and is more modern sounding. Boogie channel is based on the on the original 400+. The rest of the subway series have only 1 channel and mostly differ in the tone shaping features. All are great, so it's more a matter of what features you want/need that will be the deciding factor.
Darkglass is equally as impressive as the Mesa amps, but they're more modern and in your face. They offer 2 amps; Mocrotubes and Alpha-Omega. Both are based off their preamp pedals of the same name with the addition of a class D power section. Both have a 5 band EQ and can blend their clean and overdrive sound. The overdrive side is the part that's based of the preamp pedals. There's not much to say about the clean side.... It's a wonderful modern sounding clean channel. If you're looking at a Darkglass amp you're probably going to focus more on the dirty side. This is where the Microtube and Alpha-Omega differ. The MIcrotube is more of an overdrive sound and can switch between the B3K (modern overdrive) and VMT (vintage overdrive) voicings. The Alpha-Omega is more of a fuzz type overdrive. You're able to blend between the Alpha & Omega voicings; Alpha being punchy and Omega being over the top. On both the Microtube and Alpha-Omega you can dial in the amount of gain for the dirty side and blend it with the clean side.
At the end of my bass amp search I was just about to get a Mesa Subway TT-800 and a Microtube pedal; do the best of both worlds thing, but came across a great deal on a Mesa Titan V12 that I couldn't pass. The Titan had everything I personally wanted in one package and the deal I got made it the most cost effective. None of the amps are better or worse than the the others and I could have been happy with any of them.
*Edit* Forgot to add that I paired the Titan with a GK Neo 412 cab and that combo sound freakin' awesome and massive. Tons of punch and pants flapping low end. If you need a cab too, look at the GK Neo stuff or Mesa Subway Cabs, they're stellar. The older Mesa Powehouse cabs are great too, except the one that blends 1 15" and 4 10" speakers. That on sounds a little muddy and off.
