Hi Jeff - the hd650's are very nice all-arounders as long as you're not looking for the last word in treble sparkle. If you can conclude anything from the >1,000 pages of this thread (and the even longer predecessor hd650 thread), it is that a whole lot of us really enjoy these phones and continue enjoying them regularly even after investing in costlier flagships.
One word of caution in response to your post - I would research very carefully before choosing to invest your funds in a rsa dark star. You can purchase the boards and build a very similar amp for a few hundred dollars (see http://www.head-fi.org/t/654371/eddie-current-diy-amplifier-monolith ), and many of the electrical engineers on these boards seem to agree that the dark star design just isn't that great to begin with (one, for example, describing it as: "Thousands of dollars for a gainclone in a fancy box with dodgy anodizing"). There are a lot of great flagship amps out there. My sense, for whatever its worth, is that this just isn't one of them.