I tested the TTE800 the other day. That is a monster. Very powerful and versatile amp.
I'm vary of the 800 watt Markbass models, as the power module is digital - I find them very sterile sounding compared to the warmer 500 watt models, which have an analogue power amp. A few years ago I "upgraded" from a Little Mark II to a LM800 and was very disappointed, tonally.
The 500 watts of the TTE-500 is a very conservative spec. Markbass seem very honest with their specs - 500 Markbass watts, for example, is as loud as the alleged 1000 watts Ampeg claims for the SVT7-Pro.