I've been using 8# fireline on my creek rod for several years. Works well. The smoke colored stuff (used crystal for a while too). Longer casts and increased sensitively, plus you get a better hook set if they hit at the end of a long cast. If you are working a jig on the bottom, you'll feel a lot more than you would with mono. Not as abrasion resistant as your pline, so if you are fishing around a lot of rocks, that may be a concern. You could always attach a mono leader so the mono would take the rock abuse better.

Andrew