Dumb Head Phone Question


I am looking at a pair of Sennheiser HD 700 or B&W P7 headphones that are available through my company's rewards program.

They would be mated to an Oppo 105 and W4S ST1000 amp.

The dumb question is will I need to buy a head phone amplifier?

If the answer is yes, what technical details do I need to take into consideration?

Also, I would welcome any comments regarding the head phone choice.

Thanks!
dsper
Thank you for the reponses. It sounds like the Oppo will do at least to start and, just like everything in audio, it can be a journey.
Dsper, for a cheap thrill get one of these--you should be surprised, if not amazed, at the quality of sound. I use it with my Senn 600 and AKG 701 headsets

http://www.amazon.com/Bravo-Audio-Ocean-Headphone-Amplifier/dp/B00A2QKSVI/ref=sr_1_1?s=electronics&ie=UTF8&qid=1438439690&sr=1-1&keywords=bravo+ocean
I own a lesser model of Bravo but can attest even the Bravo V2 (also a one tube design) sounds unbelievably good, even in comparison to my SinglPower Extreme! And they cost about $80- honestly its good.
If you want what the Head-Fi community is excited about get a Garage1217 Project Ember.