Unfortunately, things move that fast. It would be nice if they didn't, but that's how they part us from our money.
what is that, moore's law? computational power doubles every 18 months.
Those $800 Dell and Gateway computers with monitor included are really poor quality. You'll likely have component lifetime issues or just defects right out of the box
i will echo that 200%. i just upgraded from a less-than-2-year-old Dell that was almost totally dead, to a new PC i built myself. i spent $800 out of pocket, but this system is better than anything i'd get from Dell by paying twice as much. i would recommend a Dell monitor, but they're on sale right now. the $100 you'd save by buying it paired with a Dell PC isn't worth it; you'll save more money in the long run simply buying a Dell monitor on sale and getting a good PC somewhere else. just buy one of their monitors and let them market PCs to business consumers.
Craig (whom i quoted above) and a few others were an immense help in my decision-making process as i bought the components for my new PC. one warning about building your own: zero bundled software (no anti-virus, no DVD decoder, etc.). but even still, most bundled software is crap, and the stuff i do use, i'd prefer to pick myself for optimal performance.
if you want someone to build you a quality PC, especially if price is no object, i would recommend
Puget Systems. they ain't cheap, but from what i've read their customer support is outstanding, and they'll basically build anything you want and work with you to ensure you get the PC you really want, regardless of your level of expertise. alienware is also good, but personally i can't stand their cases. they look childish to me. you can also find great deals on built systems on tigerdirect.com, and newegg.com is generally
the best place to shop online for computer stuff.
good luck!