Hi Brian; The Senn. 600s are an open back design and can be heard-- at very low levels-- for a few feet, so it might bother someone you were in bed with? But the 600s allow air flow through the cans (don't want hot, sweaty ears) and are more comfortable than the Grados. The Grados are quieter to nearby people. I haven't heard the RS-2, but it has an excellent reputation.
I use a Grado 15 ft. headphone extension cord with Senn cans when I need more distance from source-- sounds good too-- available from Audio Advisor or others.
My SF pre-amp has an excellent headphone section so I use it, but for travel I have a Headroom Supreme that will operate off batteries or an AC adaptor, and the little amp sounds excellent. FWIW, the Supreme used to be a Stereophile Class B component, and Headroom still makes it if portability appeals to you. Cheers. Craig
Both the Grados and the Sennheisers are open back designs that will leak a little sound. The RS-2 and the HD-600 are both among the best headphones available. They do sound different (I've tried both), but neither is absolutely better than the other. Headphones are very personal choice and you have to try them on for comfort and listen how they sound with your source material. If you're interested in the X-cans, I would try and get the "version 2" edition. For headphone extension cords, I use both a Grado and a Tara Labs extension cable and they both work fine-no signal loss. The Tara is a tiny bit sweeter, but I am not sure it is still made. I got it from Audio Advisor.
You might like to check out the Berning Micro Z for a good headphone amp. Its dynamics and musicality are both superb. It uses a couple 6sn7's for output tubes, which are some of my favorite tubes just by virtue of sonics.
You will get a variety of opinions about the Grado vs. Sennheiser HD600 headphones, but I will quickly crawl out on a limb here and state that the HD600's are the best headphones I've heard except for the Stax Lambda, which cost a LOT more money. I've owned a number of headphones over the years, including several Koss models, Stax SR-80 electrets, a Grado, and 3 models of Sennheiser. I think that Stereophile picked the HD600 as one of the components of the year in 1998 or so, and I think they were a deserving choice.
You should search some of the comments on www.head-fi.org. I am using a Headroom MOHR, Theta Cobalt, CD-3400, Etymotic ER-4S or HD-600 (best of both). I used to use Grado 325's, but now choose the 600's with the Red Jaspis cable. BTW that system for around $1500 invested is a great value, good luck.
Like Sd above, the Senn. 600s are the best 'phones I've heard too.
In my above post, I should have mentioned that the Headroom Supreme amp makes an excellent headphone amp for home use too-- as well as for travel. Great versatility, and it's small. Good Luck. Craig
In my previous post, I should have also have stated that the Sennheiser HD600's can be purchased new for $300 (I think that was the price quoted in a recent ad by Headroom). Given their excellent sound quality, that makes the HD600's a real bargain as well.
I second Thorty40 on the Berning MicroZOTL for the headphone amp. It is superb.
Actually, you can do as I did and buy new from a poster here on Agon for about $240.00. They came thru just fine and I'm very happy with them. My other recent phones were Stax Lambda Pro Jr.
I use the X-Cans v.2 with the HD600's, and can recommend the combo. The MF amp won out over an Antique Sound Labs MG Head DT during my in-home auditioning as being more dynamic, extended, and neutral, if a little more "in-your-ear" up-front in presentation. I chose it because I value the more accurate, less colored sound. (Both of these tubed amps did a better job than the output jack on a CD player.) When I previously auditioned the RS-2's on a McCormack Micro headphone amp, I found the Grado's much less comfortable, and too bass-heavy and slower-sounding. Some might call them tonally "richer", and I can sympathize because the Senn's do tend toward detail over fullness, but I favor their overall balance and resolution. I am thinking of trying out the new Cardas replacement cordset for the 600's, which is a standard 3 meters in length, but haven't used an extension.
I have tried the Grados and Sennheisers with the XCan and XCan 2 amps, and did not like either combo that much. I finally settled on the 600s for phones and a Headroom Max for the amp. I have not yet found anything better.