I have those same headphones too, albeit they are now close to 20 years old IIRC. The leatherette is worn but the headphones still sound pretty good when I have occasion to wear them. I haven't been able to find anything during my last few shopping trips to match their quality without being stupidly expensive.
My desktop speakers are an Event Tria setup, project studio grade gear, and it's been just great for the 15 years I've had that. It's pretty flat, and non-fatiguing. I have an outboard firewire box to power them, again - project studio grade. You can mix tracks on this setup and be pretty sure it will ok on most systems.
My AV gear is mid-range Yamaha 7.1 receiver and a 5.1 setup (sans the centre for now) of Australian made Subsonic speakers which sound terrific for the price - about $3700.
I'm no audiophile, so it's just a regular silver coated set of cables for the speakers.
I love audio, and it gives me pleasure every time I play a track, hearing all that extra detail and definition that spending a decent amount of cash can provide. My last setup lasted 15 years, this should last as long or longer. Money well spent over the long term.