Looks like you have been looking pretty hard to find a good deal. I'll give you some links to where I usually look for good deals (maybe you can find what you need in the budget you like).
* Slick Deals (computers)
is where I usually start. No good deals at the moment, but this can change.
* Dell Outlet
for the latest refurbs or even scatch and dents. The good ones go quickly, so if you find a good deal than jump on it.
* Tom's Hardware sometimes has some deals listed on the front page too, so keep an eye out there too.
With that said, I would stick with the Dell XPS line/HP Envy line (I'm somewhat familiar with them). You have selected those, so I think your going in the right direction and have selected pretty good systems for the $. If you have a week or so before you buy, you can usually find a good deal on some of the sites I've listed above.
P.S. I would stick with at least a 1600 x 900 LCD screen at the minimum (especially if your doing PS or the like). Full 1080p screen would be better, but is extremely hard to find in your price range (unless it's a refurb or scratch and dent model).