I've been running an Audioquest black and a red for some time and to be honest they are both very good for the money. For your computer audio needs I don't think for the money your going to get much better. yes the Shiit will sound better but I honestly think your speakers are your limiting factor. I would spend your 600 and then some on some better speakers. near field you will always lack depth to some degree but some speakers do it better then others.
I like the PSB alpha 1-100 speakers and matching sub but there are many to look at that will do a better job then the B&W's. you may even look to used and get a small integrated and separate speakers.
A friend has one of these for example and its killer for a few hundred.
match that with a set of speakers you like and you have a nice starter/desktop system.