It sounds like you want a cartridge that's easy to listen to over the long haul, understated rather than overstated. There's two that come to mind that are both off your projected budget by a bit: the Sumiko Celebration at $1500 and the Shure V15MRx5 at $300.
Don't scoff at the Shure: if you check TAS reviewer systems, many, if not most, use the Shure on their reference 'tables, regardless of price. I've compared it to many, and whenever I put it on as opposed to the rest of my cartridge collection, I simply spend hours listening to all of my records, and leave it set up for months. Cartridges that excel in certain areas tend to make you play only those records which are very well recorded, restricting your collection. Curiosity drives me to the rest of my cartridges, MCs and MMs, to see what I'm missing. And while the Shure is not the most detailed in the world (don't take this to mean it isn't, though), those instruments it captures, it captures perfectly so you think "Ah, so that's what it is!" This cartridge has incredible bass, is tonally accurate, and gets the rhythm right, so you just don't care, it sounds "right".
The Sumiko probably ups the ante. Otherwise, the Grado is very smooth, quite detailed, while being dynamic and never harsh (I own one of these as well), and excels in the midrange, but is still quite good at the frequency extremes. On the right 'table and system (unfortunately not mine: make sure you have an excellent MM phono stage), it is musically astonishing, makes the hairs stand up on your body, a very rare experience. Sumiko has their heart in the right place - music at a good price - it would be interesting to see how the Blackbird stacks up. All the other cartridges mentioned here sound good as well, and I will likely buy a Dynavector 17D MkII soon, to add to my collection. An embarrassment of riches, but I include the Shure because price isn't always an indicator of quality, and it may in fact be the best in the world at not interfering, and making everything sound equally good. Technicolour is fun, but gets tiring in the long haul (which is why I keep my Shure). If you go for the Blackbird, post a review/discussion!
