Hey all, so I've been researching the differences yet still would like more input. Currently, I have the HD 598, HE400i and a 712 Pro showing up tomorrow hopefully, though it was supposed to show up last month too.. lol. I'm using a Creative X7 as an amp/dac and ordered 4 new op-amps, and have a Little Dot 1+ on the way with M8100 tubes and a op-amp upgrade. I game a lot, and watch a movie every 1-3 days. I've also started listening to music WAY more again since I got my first pair of proper HP's. Currently, the HE400i are my music/movie HP's while the 598's are for my gaming. I expect the 712 to replace the 598's for gaming, maybe even for movies and some music. So then I plan to sell the 598's and go with the 600 or 650 (or of course the 6xx on massdrop). Any input from people who own either both the 600 and 650, or one of those two Sen's and one or more of the HP's I own would be greatly appreciated.