Your question is too vague. Start by telling us what you want to do so we can help you balance out the performance of various parts of your system. For example, if you intend to be serious about gaming, your video card could cost several hundered dollars for one with blazing frame rates. If gaming isn't that important, you can get a card with the same resolution and save some money to spend on something else.
Do you want/need an LCD flat panel? If you have the desk space and depth, you'll get a better picture for less money with a good CRT monitor.
Do you intend to burn DVD's? If so, a good burner will cost more than a simple player or a CD-ROM combo burner that will play DVD's, but only burn CD's and CDRW's.
Do you need a scanner or anything else? Every item costs so there's no single answer at a $1,000 price tag.
If you can't afford everything you want, now, start with a good, strong system. You can always add peripherals to a good, stable, reliable system, later, and it won't let you down. OTOH, if you cheap out on some basic component, such as your motherboard, you'll probably regret it, later, when you need the extra performance or reliability.
Don't worry. For $1,000, you can put together any number of really sweet combos. It all depends on what you want it to do, first. 🙂