GA pilot reported an NMAC during cruise in MCO Class E airspace requiring evasive action to avoid a possible collision.

Narrative

I was northwest bound in cruise flight level at 2;500 ft when I got an ADS-B traffic message; however my volume was not set correctly and I couldn't hear the what the warning said; all I could hear barely was that some alert had popped up. I looked down to try and figure out my volume and see what the alert was for; saw it was a traffic alert; and then looked up to see the aircraft passing directly in front of me. I pitched down quickly to increase the separation distance as I passed under their flight path. Upon looking at historical ADS-B data I found that the aircraft had climbed into my flight path from the east. I think the climb resulted in the aircraft being below my engine cowling from my point of view until the last minute; and caused my traffic alert system to think they were no conflict until it was too late due to their changing altitude. I was monitoring the local approach controller; although I was not actively communicating with them. For future I will certainly be picking up flight following on all cross-country flights.