I think the "firm" line brushes are just re-branded Rooneys, sold at a higher price.You'd be better off just buying from a vendor like VintageBlades, or ClassicShaving, and saving yourself some money, while getting the same brush.
To answer your concerns about quality: Rooneys are fantastic, and my favorite brush is my Rooney 2/1. There seems to be a general consensus around here that they are some of the best quality for the money. Extremely dense, soft tips, and great brushes.