I can safely say you can scratch the T51p off your list if you want HD800 portable sound.
It does sound fairly good but NOT reference grade good.
Sure (not Shure) you can read a lot of good comments on them but you can find an equal amount of good reports on almast any headphone.
I use an EQ'ed DT1350 which has is good and bad points but it ain't no substitute for HD600/650/700/800.
You could consider an AZ modded PM2 ?
Of course there is a price tag but if you can pay for the HD800 the AZ PMX should probably be within your limits.
The 'Tesla' bit is just a marketting phrase, there are headphones from other brands with even higher magnetic field strenghts.
To some Tesla is synonymus with peaky treble or high effeciency and neither needs to be the case.
Won't buy IEM's myself as I don't like to shove things in my ear.
CIEM's may be more comfortable but no thanks.