If you want something smoother than the Grados, try the Sennheiser range, as these are smoother, and easier going than the Grados. The downside is that they're not as detailed or precise.
I'd second the sennheiser hd650. It will also partner really well with the burson, which gives it a bit of a well-needed kick. I can imagine the burson, altho smooth, would not be the perfect partner with grados. If you want it still smoother/mellower/more midrangey, use the HRT Streamer usb dac as your computer-compatible source (i notice you say "undecided")
I'm generally not a Bose fan, but I've heard some of their headphones that I like. They sounded a bit like you've described. Hope this doesn't make me an outcast. 😳