There were two golden rules I was taught by my truck driving father; never sit at a light with the car in gear (unnecessary wear on the throwout bearing) and, always match revs when downshifting. Because..... That resistance you feel while trying to downshift (without matching revs) is the synchro working to match the relative speeds of the gearsets. You feel a lot more resistance in first gear due to the extremely low gear ratio, hence a massive speed differential between second and first gear. That is a feeling to be avoided at all cost. The synchros have a limited life expectancy, and forcing them to work in this manner will make that life very short and painful. Always try to minimize the work of the synchros by rev matching downshifts if you want them to live a long and happy life. Again, due to the deep ratio of low gear, you may even want to double clutch as you rev the engine, then it will slip right into gear. But still, I find it an extremely rare scenario (like maybe a auto-x hairpin) that requires a downshift to low gear. In two years of auto-x'ing my RS, I only recall one. It has never been necessary on the street, although I realize the smaller displacement/taller geared WRX might be a little different there.