I've heard both k701 and SA5000.
Immediate impression is build quality, much much higher on sa5000, it's all metal and a very nice feeling of cold black leather against your face, k701 is like a dirty old carpet on your face and it's made almost entirely out of plastic.
Cable is better on the SA5000, comfort is better, packaging is better, etc. etc.
Sound quality they sound nothing alike, the frequency graph is no indication, I let a couple non-audio friends demo them and they thought the sA5000 had "better bass" but they preferred the k701 smoothness (it's very smooth) so it's a more 'pleasant' listen but not as lifelike and revealing as the sA5000.
I then fed some EQ and impulse responses into a bjork track and let them compare again, and then they preferred the SA5000. Admittedly it's better at EQ and spatial effects, using impulse responses in foobar with the k701's was rather fruitless and not even half as interesting as on the sA5k's.
A note of warning is while the sA5k's can be excellent at imaging and soundstage if you feed them correctly, most of the time they're really up-front, and you can even feel like the vocalist is in your nose. Sibilance, or should I say Pierce, are right up there in the danger zone, but I don't mind them at all, in fact I find the edge and definition really addictive, but at times you close your eyes and wince during a piercing vocal or electronic note that briefly resonates in your nasal cavity or somewhere in your head.
Bass is weak as in close to zero kick but it is _really_ high quality nonetheless, I mean the bass is there in all it's excellence but the bass is really about hearing rather than feeling, you never get a bass-kick or NNNNTHSSD note in your ear out of these 'phones, the only feeling you'll get from bass is in the vibrating leather around your ears.
Coming from the SA5k's, the k701 [to me] felt like I found a pair of headphones in an attic connected to a grammophone, they were like some vintage austrian things falling apart with a very smooth character as if I was listenig to vinyl or something. The smoothness was really something imho and not like any I've heard before, but I kept noticing parts in the music where the details were missing which I previously heard, and I did side-by-side comparisons to confirm this, the SA5k's are better at revealing fine details especially in upper treble or fast accentuated sounds like a violin string or synthetic electronic tracks.
End note: If you want to listen to ballads and feel all warm and fuzzy inside and you love a decayed smooth as carpet sound, k701.
If you want exclusive upper-highs and fine-fine detail revealing in a cold, dynamic, addictive experience while at the same time excelling in natural uplifting sound with the right source or eq settings, SA5000.
Side note: SA5000's are my favorite headphone's I've heard, and I spent a limited time with the k701's, so of course my above opinions are tinted, but they are all true.