@Jeb Listens I can only second what wayne is saying about the DT1350. To me the T51p is also a bit more consumer oriented with more midbass and a bit toned down treble and better comfort. I still prefer the DT1350 overall and they pair very well with the HP-P1. And yes, the deep bass produced by the DT1350 is amazing. Not in-your-face but there when called for. Plus they work fine directly out of an iPhone, despite their 80Ohm impedance.
Thanks Plakat - it all helps me build up a good picture of the 1350. Good to hear I'll have the option of going straight out of ipod/iphone too, since charging the HP-P1 everyday requires a certain amount of dedication that sometimes eludes me. Of course the proof is in the pudding so I'll aim to get hold of a pair this week and post my review/impressions.
T51p will be the fall-back if it doesn't work out with the 1350s. Life is hard sometimes eh.