I have not heard either N3i or TD iii v2, so unable to compare, sorry.
I ordered one pair of the xtreme, but liked the foamies that come with them, so ordered 5 pairs of those. I got an extra cheap iem with the xtreme, and a couple of extra pairs of the foamies with the 5 pairs of foamies.
The bass certainly thumps with these - make no mistake. If the offer is still there, I would not hesitate. I was happy to pay 79€, but for that mad 25€ (still there, just checked), I would probably buy 2 pairs, if I was a basshead
I also listen to other music and sometimes am simply not in that same mood, so I use other IEMs and fullsize cans. I have the Denon ah-d2000 as my full size, and they are simply amazing.... but that is another story.
Good luck on your purchase.
I just ordered a piar of the TD III v2. Was wondering what kind of foam tips xears use?