Originally Posted by ChrisSlicks

It is mostly the fluid, the hydraulic line isn't under anywhere near as much pressure as in the braking system so being SS or whatever isn't a big difference. Upgrade to high-temp brake fluid for the clutch.

The line is directly next to your exhaust, so especially if you upgrade your cats or headers you will need to add extra insulation to the clutch line near where they pass the header.

I beat my car relentlessly on track, with the stock clutch line and never get a soft clutch pedal, I use RBF600 and extra insulation wrap.