What do you mean by 'waste'?
The 7506/V6 definately sounds better with an amp. ALL headphones sound better with a headphone amplifier. The question, given your current situation is, HOW much better, and is it worth the expense and hassle of yet another piece of equipment. And, how important is sound quality to you, really?
I use my 7506s with a portable SlimX mp3/cd player. It works well out of the headphone out. It sounds better with my cmoy. Not a LOT better, but definately better. I would rate the 7506/v6 as a headphone that doesn't 'need' amplification to sound good. the HD600 'needs' that extra amplification to sound good. However, the 7506/v6 does improve with amplification.
Where are you going to be using it? Portable players and mixers? It will run fine out of either, and you'll probably be happy with the sound. The portable player will show a good improvement if you add a portable amp like a total airhead or a porta corda, or a diy cmoy or cha47 or a JMT built amp, etc. However, the cost may not be worth it to you. But if best sound is your goal, then the amplifier will have to be added. If very good sound on a budget is your goal, then you can drop the amplifier. As far as the mixer, what kind of mixer are you using? Most mid-highend mixers have very good headphone stages as it is. My Allen and Heath had a great one, the soundcraft boards I've used were decent, and my mackie has a surprisingly good headphone amp, considering the mediocre quality of the rest of the board. If you have anything even higher end, like a Midas, or an API, they have headphone amps rivaling most serious hi-fi gear. So anyway, while a nice headphone amp will probably improve the headphone out on your mixer, you'd probably have to get a considerably more expensive amp to see serious improvement, and that cost is probably not worth it to you at this time, in a studio environment, you'd probably be better off putting that money toward better monitors/mics/etc.
So anyway, my recommendation for a good price/performance ratio is to get a basic portable amp for your portable use, like a total airhead, porta corda, JMT amp, or a DIY amp, and while in the studio, just use the headphone out on the mixer.
Peace,
phidauex