VGA repeater/extender circuit
Why use a microcontroller just to boost a signal ?

A simple op-amp is just what you need.

Here is the Maxim's page for Amplifiers according to the resolution (SVGA is 800x600 ah FredP said): http://www.maximintegrated.com/products/video/amplifiers.cfm

HSYNC and VSYNC are TTL signals so a small buffer is sufficient.

VGA Electrical FAQ