I currently own both the 3.ai, 4.ai, and the h300. I guess it depends on what you think of as an upgrade. 4.ai and H300 are totally two different stories with not a lot in common. There are more characteristics closer to the 3.ai rather than the 4.ai but to me H300 is superior in many aspects such as detail, clarity, soundstage, etc. H-300 has better bass extension with speed, overall mids are just on another level, and treble will be more on the analytical side than the 4.ai. I do prefer and admire the build quality and aesthetic design with the wooden faceplates on the Heirs but the H-300 don't look like they will break in a hundred years. It's a tank. Soundwise, I do think of it as an upgrade. Just don't expect a pretty glossy looking earphone haha.
Alright, I think I'm going to give it a try. Do you know how long the promotional pricing will last until? It was supposed to end 2/28, but it appears it is still going on. Once that pricing expires, what will be the normal price? Don't get my paycheck until end of this week (dat college life).,,