The K701 sorta separates the vocals from everything and puts them right in the center for you. It's not really an offensive, fatiguing can either. An O2 amp that costs $150 assembled can drive them well. I think they sound better off that amped from my sansa clip's headphone jack than with my Arcam 73 cd player and either Heed Canamp or Darkvoice 332. That Arcam player was going for over $800 brand new not too long ago. Those amps are also both several hundred dollars. The Sansa clip and O2 are both neutral/transparent and have had their measurements posted and verified, which is not something you can say about much of any source or amp out there. O2 is also small enough to use as a portable. It powers my 600 Ohm DT990 headphone quite well too.
You could also look at closed phones like K550, Yamaha Pro 400, and Amperior. I've written extensively about them in many prior threads. I've been to a Can Jam, Chiunifi, and heard many pieces of gear at stores.
I would recommend going with sources and amps that have the objective parts of their performance verified. And it's not just sound stuff. Some amps have serious design flaws too. And these things are generally not cheap. If you did go with a Sansa/O2 setup or something similarly priced, you would have $500 left to spend on phones. In my experience, spending lots of money isn't always great, it's not a sure bet. I thought a Stax SR-009 smoked just about anything I ever heard in terms of smoothness and clarity, but not in other areas. For 5 grand plus however many more hundreds or thousands needed for the amp, I expected a lot more. I never liked either of the LCD phones no matter what I heard them on. Wasn't all that fond of the $5000 Abyss phones either. I tried my RS-1 on many different setups and thought it was weird how none delivered what I was looking for. I picked the Arcam 73 for it after listening to a whole room of cd players. The coloration and soundstage of that player helped offset some of the flaws in the RS-1. But now I think the RS-1 sounds plenty good with the Sansa and O2. I was willing to shell for the RS-1 6 years ago based on what was out at the time. I would shell for a headphone I thought was perfect. Maybe such a headphone doesn't exist.
You can gamble and buy different things and hope they work for what you want. If you buy something cheap that delivers and are satisfied with owning a few phones, it might be good to leave it at that and just acquire new phones once in a while. Always demo stuff if you can. So many people throw so much money on gambles here. I wouldn't say I'm a hardcore objectivist. I'm sure there's amps I would prefer to the O2 on certain phones that don't measure as well. Finding them and purchasing would be another story. Even then, maybe just using the rockbox EQ would be satisfactory. I just wanted to present this info so you get more povs to incorporate. I've heard a lot of people drop off here after attending meets, so I try to stick around even if I'm not currently seeking any new gear.