My panel has two GRT display units, an AHRS, GNS 430, 327 Xponder, audio panel, ICOM A-200, an an autopilot that all use power and generate heat, and I have had no problem with not having any active cooling in 600 hours and two years of flying around the Texas Gulf Coast.
Of course, YMMV, and I could suffer a big melt-down any day, but I have not feel that I needed to add anything active.
Paul