I have never heard of that speed controller but it's 120a so should work. If you are looking at running buggies then 4.0t is way to much, I would go for a 7.5-8.5 for a 2wd buggy but a 6.5t for a 4wd. That servo is a good one so yes.
Motor
http://www.apexmodels.com/gbu0-prodshow/SP13865V3.html
A very good speedo at a good price but wouldn't run anything lower than a 6.5
http://www.apexmodels.com/gbu0-prods...T98802LPB.html
Or a very good one for £30 more
http://www.apexmodels.com/gbu0-prodshow/SP000222.html
or
http://www.apexmodels.com/gbu0-prods...EXT98802B.html
If I was to pick I would go to the Reventon Pro as I run one and it is a brilliant speedo!
Sam