Why you would trade your HE1000SE for the Diana Phi ? neither sound or comfort is better , anyway if you still insist in the trade , i would say the Diana Phi should be demoed before buying , my brother had no problem wearing them (he has huge head) , but for me it was uncomfortable , i had to put some pads so the ear-pads match my ears , also the headband doesn't have any padding so even if it fit you perfectly you still need some pads under the headband for more comfort , size and weight was OK , but not outstanding , build quality was perfect and way better than the HE1000SE.
The diana phi is a great sound headphone. It is different than the he1000se. It has more resolution and way better build quality. It also gets you almost 90% to the sound of the 1266 phi and maybe 85% of the 1266 phi tc.