good headphone amp/preamp?

If you can wait awhile and maybe extend you budget, the Burson H-160D would work. It's brand spanking new, got great reviews, fits your needs but retails for around $1100. When partsconnexion.com starts to sell it, it will go with a good discount. They don't carry it yet but they do carry all of Burson's other products. Having said that, the Burson headphone amp is around $600 by itself.
Another one is Schiit (let the puns begin) but its a headphone amp only, in SS and tube versions and has gotten great reviews as well. Its made in America as well. Here is the link:http://schiit.com/
The SS goes for $249 and the tubed version for $349. They are class A devices and the guys behind it have been in the business for quite some time.

I have been using an Earmax tube amp with my Senn 600s for a long time now and have no complaints . I use a Van den hul interconnect and Cardas headphone cable . I sometimes run it direct to the source for a more direct sound or through the main preamp for a softer smoother sound . My musical tastes are very similar to yours . I'm sure you could fine an Earmax used for under $500. Happy listening

Thanks for all the input. Got some things to chew on here...and I need to get it right and think about how it will get the most use. Have bought too much stuff in the last year searching for improvements and its sucking up space and money.This issue of listening with phones only recently came up due to new neighbors so it has thrown me off course.

Don't you just love new neighbors?
Its hit or miss when you live in an apartment like me. There are some room treatments you can do that might tame the noise unless its late night listening you're alluding to.
Good luck, and mind your ears with those headphones.

The Woo Audio WA-6 is really exceptional.

Haven't heard it, but what about the new Musical Fidelity M1HPA? (http://www.musicalfidelity.com/products/M1-Series/M1HPA/M1HPA.asp)

MF is usually very good, so I suspect that it would be a good choice.

I would look at Woo and Decware. They may be a little above your budget but resale value is very good on headphone amps and many have preamp outs. You might also pose this question on Head-fi, where headphone junkies hang out discussing the latest and greatest giant killers in the world of headphone amps. I am sure they will recommend something within your budget.

Mcondon, thz for the tip on Headfi....apparently I have lived in an isolated world.

Head-fi is another world, but be careful. There are still a lot of folks over there who are pretty hung up on specs or topologies, or boutique part count rather than implementation. Oh wait.... I think I posted the same thing over there once, talking about Audiogon ;~)