Hello, first time poster. A little history, I got interested in putting together a headphone system after browsing a thread on a different forum where members posted pics of their headphone rigs. These ran the gamut from entry level to high end, it was interesting reading, a new world of audio I had not explored yet. Then I came here and explored for a few weeks for some education. Last week I found a set of lightly used HD 600's on CL and decided to take the plunge. After some haggling I got them for $175 which I hope was a decent price. They look new, no chips/scratches on the headband, cable like new, pads show little wear. Now that I had some headphones I decided to go full steam ahead and get an amp. After reading what seemed like a bazillion reviews/impressions here I ordered a Valhalla last Saturday. It's back ordered so I've been listening via an Oppo BDP-83SE --> Pio Elite AVR in the mean time. The AVR seems to drive these OK but being a complete noob I can't say that with any authority, but I'm liking what I'm hearing. I read that the HD 650 cable is beefier and some say better sounding so I ordered one along with a Mogami 10ft extension cable. Neither has arrived yet. Any opinions on the Mogami cable? Well that wraps it up for now, I'm going back to get acquainted with my 600's.
Great story and first post. I can relate with where you're coming from. You have a nice setup! I also have an Oppo BDP-83 (not an SE) and a Pioneer Elite SC-25 and HD600's. I connect my Oppo via HDMI to take advantage of the Pioneers wonderful Wolfson DAC. I have found the headphone output of the AVR competent, but not really noteworthy. The full frequency range is there and everything sounds pretty neutral, it's just a little flat and lifeless. So do you run your SE to your Pioneer via HDMI? That would allow analog connection to a dedicated headphone amp - no DAC required because the SE already has a good one.
An external amp will definitely help, but in my opinion, don't waste your time with tubes. I think buying a tube amp is like buying a restored 1967 Camaro. It looks cool and turns heads, but a new Honda Accord is less expensive, faster, corners better, stops shorter, is more comfortable, is more reliable, and gets better gas mileage. The Senns are pretty easy to drive so you don't need a huge amount of power - a well designed solid state amp will serve you the best.
As for aftermarket cables, they're an even worse investment in my opinion. They are like those magnets you can buy to put in your gas tank to "align the ions" in the fuel to improve combustion resulting in increased horsepower and fuel economy. Don't drink the snake oil - the cable that came with your HD600's is all you need.