Anything over a 1A charger is not going to charge this particular phone any faster than the stock OEM charger.
The 'quick charge' feature which is available on the SNAPDRAGON 600 chip was disabled for this phone,presumably to keep battery charging temperatures to a minimum, to prolong the serviceable life of the battery.
However,some are reporting quicker charge times w/the latest update(s) that have been pushed to the HTC ONE,although no official documentation/statements support this.
Gonna see if there is such an app in the GOOGLE PLAY STORE that will record/notify of charging time(s).
The battery in the HTC ONE is of LITHIUM POLYMER construction,which is said to have a longer serviceable life vs LITHIUM ION.
I wouldn't worry about it,as the phone has a 1yr warranty. Should you find a significantly measurable drop-off in battery life,file a warranty claim.