I haven't been an avid descriptor of anything headphone related before, so excuse me if any of this sounds "wrong," or overly simplified.
It's difficult to say whether or not the HD800 would be a tangible upgrade. To my ears, the HD800 is the most luxurious, wonderful headphone I've had the joy of owning. If anything, it has even given me a greater appreciation for my other headphones, in the sense that I can really understand what each headphone's sound signature brings to the table. The HD800, for me, has most of my favorite characteristics of the headphones I own;
The space/air/detail, if not greater in this regard, of the AKG K701s, with a smoother, not dry presentation
The bright, but not fatiguing feel of the W5000s, with greater bass quality/quantity (not to say the HD800 is a bass monster by any means, but it has the "correct" amount more bass to me to really bring together the music)
The transient response of the Stax SR-007A O2, and again smoother
For all three of these, I feel the presentation of the vocals in the HD800 is also better. They end up more focused in the mix, and so detailed it's almost like you're there where the vocalist was when it was recorded.
This is usually with the HD800s run from a Woo Audio WA6 with the pseudo dual power supply, which is a relatively inexpensive amp considering the quality. I feel it's a wonderful combination. I have a Headamp GS-1 in the making, and as most people who have dealt with Headamp (or even those who have just read about it) may know, that takes time. But I should have that within this month or the next, as I was told. I feel that may potentially run the HD800s better, but if I had to settle for the WA6 I wouldn't have any trouble, and I can't make assumptions like the GS-1 being "better" until I can live with the equipment. The GS-1 is often described as "wire with gain," and with a Red Wine Audio Isabellina DAC arriving to me within the week, I will definitely have the source for the GS-1's potential to be discovered.
This isn't to say the DAC in my CD player isn't worthwhile. But with it, and with the aid of the HD800 (and the O2), I've come to realize that there's a bass/midbass leanness and sterility in the onboard DAC that I feel is holding back the headphones from their fullest potential.. so that's something to think about. The source is a very key component of the chain, and the HD800 is very sensitive about the chain.
Thus, while an HD800/amp may be a worthwhile purchase, if you're willing to drop the money for the HD800 then you may also consider having a worthwhile source. As it sounds like you run off your computer, I'd consider looking into a usb DAC/amp combination, such as the Benchmark DAC1/Grace m902/RWA Isabellina HPA/more, but my memory's a bit shaky right now. You'll notice these all fall into a similar price range around the price of the HD800 as well. So it will be quite the investment. But from my perspective, I find it to be a very worthy upgrade, as at this point, I feel like I could sell everything else I own to better my HD800's synergy with my equipment. I don't intend to scare you with this thought.. again, if it hadn't been for the upgrades I'm attempting with my components, I could live with what I have undoubtedly. Even with the way I've recognized my CD player's DAC "shortcomings," I am still entirely pleased with what I hear, and there's really nothing stopping you if you can feel the same with what you have.
Again, this is if you opt for the HD800. There's always a whole world of less/more expensive equipment that will all have different presentations/colorations to the music that you may or may not like. With so many options, it's hard to really say item A has greater integrity than item B or vice versa, especially with everyone's varying tastes. But if you feel like the HD800 may be what you're looking forward to, and you're willing to take that option, I would do it.. the mental satisfaction alone from going with what you felt ("placebo effect") could be just what you need. I feel I may receive flak for that comment, but I'm no purist. I just enjoy music.
EDIT: For clarification, I don't mean that as an attack on anyone here. I don't think anyone would have the equipment they do if they didn't enjoy their music as well. But I feel that the HD800, even just to try it, is a solid investment because even if you don't like it, it's so easy at this moment to make back a lot of what you spent for it if it turns out to just not click with you. So if you feel it, and will give it the chance, by all means I would suggest giving it a shot.