8 years ago, paying $3000+ for a good computer was quite common. In fact, in order to get top mid-range components and a system that would last for a few years without upgrades, it was necessary.
Things have changed, although the market wouldn't like you to think so. Even the most basic modern computer parts allow for fast web-browsing and application use. A good system with 2GHz processor with 512MB RAM and an 80GB hard drive can be had for $600 now. Double this to $1200 and you have a very good gaming computer. Even if you want a top of the line gamer, sporting the best and smoothest graphics, you'll be hard pressed to spend more than $2000 if you buy wisely.
The problem is, Intel still has their Extreme (EE) series CPU out for over $1000, AMD's FX chips are still close to $1000, nVidia and ATI released $700 graphics cards, which fools will still put in SLI ($1400) to get way more than they need. Hard Drives are up to 500GB (I haven't even used 20GB of my 80GB drive). When you put all these components together, you get a $4000+ system, and it's only going to perform 5% better than that $2000 system we just looked at, while costing 100% more. In fact, it's only going to perform 20% better than the $1300 system, while costing 150% more.
What do you do? Well, lay low and upgrade only when necessary. Don't be fooled by these top-of-the-line parts that are just there to make money, because they will still be obsolete in a year.
Core: Get a mid-range dual-core processor, it'll be worth it going into 2006, and single-core chips will be obsolete by 2007. Start with 1 to 2 GB of memory, and a "small" 80-160GB or "mid" 250-300GB hard drive. Don't pay a premium for 400GB+. Even power supplies are out of control; you don't need more than 400W if you're only running 1 graphics card. 350W is fine for most of you.
Video: For your video card, there are a ton of choices. I prefer nVidia right now, but either way, keep yourself between $100 and $300. Nothing else is worth the price. For your monitor, that's up to you. With a mid-range ($150-200) video card, a 12ms 19" monitor for $250-300 works perfect for games at 1280x1024. If you have a high-end ($250-300) video card, go ahead and buy that 12ms 21" monitor for $750-800 with 1600x1200 resolution. It's the best you can get and one purchase that's truly worth the money.
Audio: For audio, avoid the X-Fi cards for now as I hear they have gaming issues with some modern games not designed for them. Stick with your Audigy 2 ZS or onboard if it's better than the Realtek ALC850 chip. And these speakers sporting 500W-700W of power. I have a 200W system and it's way too loud for my apartment. 100-200W total is plenty.
Follow these rules, buy in moderation, and your total system cost will be between $1000 and $1600. And you'll be able to play all modern games on high settings. Be ready to upgrade your video card (another $100-300) in 2 years, but so what?
Get that $3000 system and you'll have the hottest system on the block, for 6 months, until the next person wastes another $3000 on buying the new hottest system, and so on. You could spend $3000 on a computer, and still have to upgrade the video card after 3 years, or spend $1300 on a computer and upgrade the video card after 2 years. Hmmm...