How often are you loosing a side torso early? An XL300 would get you big bump in speed, although admittedly there are risks.
I've stopped running XL engines in any non-clan medium, heavy, or assault - it's just too risky. I've lost a side torso in most of those games, with around a third of the total damage being done after that. Most people will aim for the pods, miss, and hit the side torso. That, and speed hasn't really been an issue.