Seriously, if you like the HD598s' wide soundstage then you will be very disappointed with the HD600s as well as the HD650; but their bass may be enough for you. I owned both the HD600s and HD650s at the same time almost 2 years ago so I'm pretty sure about that. And the HD800s' bass is far from weak especially when being compared with the HD598s unless you are trying to use them with an iPod or some cheap portable amps, because these high impedance headphones need serious amping.
To be honest, I've owned a lot of Sennheiser headphones from the cheap earbuds MX470s to the current flagship HD800s so I think the only Sennheiser headphones which can meet your requirements are the HD800s because of these following reasons:
- They are so fast that they can reveal all minor details in fast-paced music like rap and hip hop.
- Their clarity is only second to that of electrostatic headphones like the SR-007s or SR-009s
- They have the most well-defined type of bass, compared with any other Sennheiser headphones.
- They have the widest sound stage and the best imaging of any current production dynamic headphones (which is crucial for gaming of course; I play CS:GO too).
Don't even bother to find these characteristics in the HD600s and HD650s. The HD700s are superior to these 2 but.......
But like I said, the HD800s require lots of voltage because they have very high impedance; so you should consider buying an amp if you're ready to spoil your ears with the HD800s.
And btw I prefer using the LCD-2s when playing CS.
The HD700's are not superior to either the HD600 or HD650, They have too much treble emphasis, to the point of being fatiquing. The HD800's do not require all that much voltage to drive as they are more sensitive than either the HD600's or HD650's. They are sensitive at102 db/mW so 63 mW or 4,35 V RMS will drive them to the threshold of pain (120 db SPL). A FiiO E12 portable amp will drive them way past that. There is way too much myth floating around the Internet. I seriously doubt that the soundstage of the HD600 or HD650 would be dissapointing to a HD598 owner. I have an HD558 with the black foam mod (so very similar to the HD598, same transducer) and the HD600 is not blown away by them. I have the HD600's as well.
I will say that the HD800 is an awesome set of cans.