I have 7 pBass (4"-5"), 1 Silver Aro (8"), 1 flagtail (5") and a fire eel (12") in my 65g. I have an external filter, nothing extra powerful though. I do water changes twice a week, 60% change each time.
My tank doesn't look crowded still. It will when the pBass add couple more inches though. My target was to move to a bigger tank when the Aro hits 14" size, but my 220g is in the process and should be ready in 3 weeks time.
I also did not do fishless cycling for my tank. I put the fish in the same day I bought the tank. Continued with 30% water changes once in two days for few weeks and now settled in to twice a week.