Is there a problem with video quality with both connections when using the VGA splitter? Does the video look okay on both connections with the splitter out of the equation? If so, then you should try using a VGA switch instead of a splitter.
As was mentioned, the use of a balun might cause video quality to suffer over a long distance. You might want to consider using an alternate method for getting video to your monitor from the switch (e.g. wireless VGA adapters)