As indicated in my last post, I bit the bullet and went for the cheap-as-chips (as headphones go) Koss Porta Pro headphones. First impressions of the sound stage are good, decent detail and plenty of bottom end without being invasive. The bottom end is just a touch muddy but it's far from being "bad". I'll given them some burn-in time and will repost if the character changes significantly. The build quality is a bit flimsy so the set will have to be treated with care.
Thanks for all the info and suggestions. All of the phones mentioned have been noted for future reference if/when I look for a higher spec pair.