Accurate timbre means its ability to reproduce sound very close to its real life counterpart.
The general gist of that review, is that the dt880 is the most accurate headphone for that reviewers type of music vs actual instrument experience.
Electronic music doesnt require the accurate timbre of musical instruments because all of the sounds are synthed to begin with, so the increased speed that the sa5000 as well as arguably the detail would put the sa5000 above the dt880 for that particular type of music.
In my own personal experience I love the dt880, driven properly, it has bass and mid bass that is full of body, smooth mids, and extends reasonably in the high. Detail is good, but not as resolving as say for example my ms-pro.
I haven't tested the sa5000 yet, but my reading has me believing that is may be sonically similar to the audio technica series. It may or may not be, so take the next passage to be about the audio technica ad series with perhaps some relevance to the sony.
I have owned the Ad900 as well as exstensively demoed the ad1000 and ad2000. I won't go into the specifics of each one, but this phone family has its sonic signature tuned to the upper end of the sound frequency, with a very light bottom end. Many people say that the sound is very "airy," whilst I agree I would add that the sound is also very hollow. This is not necessarily a bad thing, I quite enjoyed it, I found it good for music that was predominately female vocal, as it added a very nice "haunting" feel.
I know you already own a couple of pairs of grado, however, maybe entertain the notion of possibly checking out the alessandro ms-pro. Of my headphone experience I'd say these are the most versatile, and their ability to resolve guitar is amazing, which is important for most of your musical genre's. I find that they are slightly aggressive in their sound, but not overly so (definately much more than the dt880, the audio technica's and the k701.) Whilst for myself this does translate into some harshness and fatigue over time, it also provides alot of "energy." However I still find that they sound appropriate at all times, ei, the energy does not affect quiet passages.
Next we come to the k701, I've only had the opportunity to a/b these against the dt880. They were amped, though amplification may not have been the best. If it sounds like I'm making excuses for the k701 I am. They have a wonderful soundstage and reproduce sound in a very flat detailed manner. They sound good, but not great, whilst they did resolve better than the dt880, when a/bing them one thing becomes very apparent, the bass. If it were not for this one let down, I would put the k701 above the dt880 purely because of the extra detail that it allows. However, the bass, even though its there, seemed completely artificial, and coming from the dt880 it was apparent that it was actually "bumped" however not even bumped to increase its volume, bass seemed like it was being forced into the mid bass region, making it sound unnatural, the lower extension just wasnt there. Also there was a distinct lack of body. Keep in mind that this wasn't say, the bass leaness of the audio technica's, but just a very tonally inaccurate and for me unenjoyable sonic characteristic. Once again, keep in mind that different amplication may have changed my mind on the matter.
The best advice I can give, is to try to find a place that has at least a few of the aforementioned models so you can do actual comparative tests. With your amp if they let you. Or if you are bugget conscious, go 2nd hand, from my trawlings of the forums, it seems like the dt880 and to a lesser extend the k701 is your best bet in terms of price and availability.
. I listen a lot of stuff, mostly jazz (especially Latin), classic/light rock, classical, Spanish guitar, some metal, and electronic music as well; a good portion of it is lossless. 
