most of them will make ur ears sweat after long hours of usage, if the pad is leather or very tightly knitted cloth like from shure's that is

i had shure 440 and yes i sweat my ears, but beyer dt440 won't, so is subjective matter

lightning or 30pins 

A very obvious YES~ 

Tested X3 with HD650, I personally do not like it at all. The sound has no strengths that attract me. Even X1 was doing better with its faster and more energetic sound signature, which feel good. X5 has better sound stage in comparison.

I seriously suggest Cayin N6 if you want to skip amp. It is the player that I am looking at now... But costly... 

Cayin N6 more than RM2k as I asked around. Kind of dissapointed with Cayin for 2 things;

(1) Crazy asking price. It is more than most headphone. That player is just so small and charge people so high... Siao. 
(2) I do not like the looks 

But I really love the sound... Even no amp, I cannot find any complains with pair with HD650... Really good.

Since you pairing with HD800, I think you should get at least this Cayin N6 la... I am only using cheapo HD650... Thus cannot afford the good player.

Btw, I found this N6 sound way better than all the DAC/Amp that I tested with my phone as source. That include the C5 and Fiio Kunlun.

It seems there are some hidden secret in the N6, which more than just the lots of op-amp... I do not know what it is... But it certainly sound good and I like it.

1k amp (phone as source) also lost to N6 kao kao... even same brand from Cayin... I dunno why.

You go hear la. Uncle is very friendly there.

If you dun like N6 for any reason, you know where to let go man... I am waiting...