Yours must be 1998, which i believe was the first year Marin offered these Billato bikes.
Here's the (almost similar) bike from the next year.
Different fork/stem.
Mega Tube was the name of the shaped Brain.
edit: Bought mine, the 1998 version with quill stem and curved fork, in late summer 1998 for $899. The next bike down the line was a Thron tubed bike with Mirage group for $799 on close-out.