ThomasTrouble - I'd find it very hard to conceive that anyone would be disappointed with HD800's. If you were you could just return them. If you go past the return period you can very easily sell them for only a few hundred less than you bought them if that - they will sell very fast on headfi.org. No experience with that amp though. Let us know what you think.
Scottmac - I've only heard the PS1000 once before and was very impressed in that brief exposure. I had not heard the GS1000 at that time nor the HD800's, so I resisted making any comparisons. If memory serves they were a bit more punchy and rich, while the HD800's could be slightly more 'airly' and occur to me as effortless in their presentations of various types of music. Again, that is from memory. No doubt the PS1000's are fine cans. The HD800's presented a sound I loved at first listen and had to have it. That did not happen with the PS1000, but I think that could be entirely a case of personal preference. Another more economical can (around $600) worth looking into are
HE5LE's. I tried a pair of their predecessors and was mighty impressed, especially by staging. Ultimately I found them a bit too aggressive and sent them back within the 30-day trial period. The LE supposedly does away with certain stridencies in the original. An HE6 is in beta currently. These cans require a powerful amp to work well. Their own tube amp supposedly is a good match, but not the only way to go. Just don't try them with any headphone amp - these need at least 2 watts - check user reviews for appropriate amps to use.