I upgraded from a SWR Headlite to the Little Mark Tube 800 after buying a 4x10 104 HR and wanted a head to match the cab. As they're both rated for 800 Watts, it seemed like a perfect match.
Out of the box, the Little Mark Tube 800 is built like a tank, there's a QA sticker from the MarkBass factory indicating they've tested it which is reassurance of the overall quality of the build. It has side mounted 4mm rack screw holes if you want to rack mount it too.
From the front panel, the power switch is sturdy (My SWR's failed after a few years), and the controls are intelligently laid out. I had to use a Boss EQ Pedal with my SWR to get the tone I wanted. Using the combination of Bass, Low Mid, High Mid, Treble and the built in filters on the MB, I was able to dial in my tone very quickly.
The one thing I would change on it is the master switch being a pull to mute, it's awkward, and the design of the knob is too smooth making it difficult in a dark stage environment. A small push switch would have been more beneficial with illumination to confirm.
Rear panel is awesome, proper switchable DI, large fan to keep things cool inside, effects loop and tuner out - which I can't imagine anyone using TBH.
I'd highly recommend the amp, I can't believe the ease of which you can dial in your perfect tone, and the overall power of something so compact!