Now, I've seen everything. J/K Actually, I did the exact same mod on a 12 port 3300 Switch. I put one Panny 1A and a no name. Both are quiet but as with all low rpm 60mm, they don't push much air. If your doing a 16 port version, evaulate the unit carefully. The ICs controlling the ports can get pretty hot causing the ambient temperature to rise significantly. The two fans, like the old ones, blow air out but at a reduced CFM and dB. The air is warmer though. Anyway, I've been good for 3 months so far running 24/7. However, I would never _NEVER_ do this with a workplace unit.
1. becareful removing the cover.. it's a bit of a pain just don't use too much force as to not break the latches
2. YOu'll have to remove the Power Supply PCB in order to secure the new fans with the plastic screws.
Other than that, you (we?) should be fine. I hope... Time will tell but again so far..so good.
man I love this site