[Dadracer]

Just a thought but has anyone found a pair of headphones which image really well and produce an excellent sound stage but which only have a single cable to one ear piece and not one from each?

 

[Amarphael]

Beyerdynamic T90 has these qualities that you seek, I can attest as a happy owner.
AKG K812 also comes to mind, though I didn't listen to them yet.

 

[Melrose]

AKG K240 on the low end, and Q701/K701 on the higher end. AKG is known for soundstage and clarity, and have one-sided cabling.

 

[viralcow]

My vote goes to the Audio-Technica AD900 for less than $300.
 
Replace the stock pads with spare W1000Z ones for more bass (can be ordered from AT for about $25).