If you haven’t already, I highly recommend taking a look into using LibSass (a C/C++ port of the Sass engine) to compile your Sass files.
LibSass doesn’t do much on its own (it’s just a library), it requires an implementer. This is where SassC comes in: it provides a wrapper application around LibSass which allows you to compile Sass files from the command line. And because it is also written in C, it is also lightning quick. Out of curiosity, I measured the time it took to compile the main stylesheet of one of our new builds (which contains nearly eighty @imports) using SassC, with the following command:
time sassc scss/styles.scss > css/styles.css
The result was 599ms. Pretty impressive, huh?
The only downside is that you need to compile SassC from code. However, its GitHub page provides detailed instructions as to how to do this.