In terms of "hi-end" (what is your budget exactly?) cans, my recommendation would have to be GS1000 (£850) which have set a new benchmark for headphones... unless of course you are talking the highest end of the spectrum where the Sennheiser Orpheus (£10,000) would come into play...
Of course if you are a mere mortal like me and consider the £250 mark hi-end then you should check out the Beyerdynamic DT880 or the Sennheiser HD600 as suggested above. As always, it is best to test as many of the cans as you can in your budget. As for headphone amps... Graham Slee Solo, Creek OBH-21 SE, Grado RA-1 all spring to mind but all depend on your budget...