I had an old hot end for 1.75mm filament. I am using 2.75 mm filament so i prefer to buy a new one, because mod the old was more expensive.
In my opinion [url=http://Hotend V2.0 for Delta]Hotend V2.0 for Delta[/url] is the best one. It has air diffusion ,it is stable and it is made for working for many hours . That was my thoughts before i buy it and all was reall. I made a new x-carriage .
I have to say here , hot end need modification to pass through x-carriage hole, it is really easy .
I add two fan 30mmx30mm, one at each side and voila!!
But, with this hotend z height reduced from 90mm to 70mm . Unfortunately
Cost is around 50 euro.