Seeker 2x was my final mini-sumo robot, designed from the start to be low, fast, and aggressive.
It was a "spare no expense" kind of project, and probably cost somewhere in the ballpark of $1000 - $1500 by the time I was done. It has an AVR ATmega128 as the processor, running C. It has two line sensors on the bottom, and a total of 5 IR opponent sensors. It is a regulation mini-sumo, in that it is less than 100mm x 100mm, and weighs less than 500 grams.
I have a lot of detail and build pictures on my mini-sumo website (http://huv.com/miniSumo/seeker2x/index.html).
This is a companion discussion topic for the original entry at https://community.robotshop.com/robots/show/seeker-2x-mini-sumo