In a no-interference environment with perfect conditions (which I'm sure you don't have), Cisco LAP access points are spec'd for 25-50 users each for acceptable performance with a "well....you can do it" maximum of 100 users per AP. Other top tier brands are going to come in right around the same figure. SOHO equipment will be much less, usually about 10-15 connections before things start getting ugly.
It sounds to me like you just have highly congested access points. I'd consider adding more, and also doing what you can to push users to 5GHz to cut down on interference.
Edit: Just as an anecdote, I deployed 2 Cisco LAP1142s to the lecture rooms at $LastJob, because they were 90+ seat rooms. This was our standard lecture room spec. The coverage was not the issue at all, but the potential clients per AP was a deal breaker, causing me to throw almost $1500 per lecture room at it.