STAX != SR-009. They make more than one product.
Also electrostats != STAX. There is more than one manufacturer.
I agree on the Denons
(the ones I've heard) - I don't know how the 7100 do or don't stand up though. They aren't bad headphones, but they aren't the ideal choice for detail extraction and pristine voicing. Of course, if isolation is a question (as currawong and I have been asking) - none of the open cans that we keep suggesting are going to be a good choice.
The original post explains what equipment is in place in terms of amplification, source, previous headphones, etc. If the LCD-2 are within budget, both the Koss and STAX electrostats are within budget too - no question about it.
I think at this point the best possible thing he/she can do is go out and try the models that are scoring highest among suggestions - if that isn't possible, a coin flip is probably going to be best (sure, we can all sit and argue back and forth what the "best headphone ever made" is - but there won't be a conclusive answer that satisfies all people).
I'll also re-iterate the GS-1000 should still be considered; if that hadn't been caught the first time. But really at this price point, trying these out for yourself is going to be the only real answer. I also think it's kind of interesting that the majority of responses seem to be saying LCD-2, HE-500, or something else; yet HD 800 has more votes by a mile. Wonder how many people are actually reading the thread before voting...