The first thing I would say is to determine what exactly you will use your future system for and then figure out exactly how much power your going to need to support your tasks. Honestly, for your intended uses you really won't need that much power. As an example, you can run Office 2000 Premium and surf the net and email at the same time on a PII machine running Windows 95 and you'll be fine. Obviously a P4 or any decent Athlon will be more than enough and will definitely prepare you for future upgrades. Now, if you wanna do video work then you might want to go with a Mac and run I-Movie or Final Cut as your video editor. Either of those two kick ass although I have a preference for Final Cut. I have to do this for work and I use a Mac there so I'm pretty familiar with this.
Anyway, to answer your question: Unless you really enjoy building computers and know what you're doing, I would go with a Dell. First, the sum of the parts on a homebuilt will come out to be more expensive than the complete package from Dell. The reasons vary anywhere from basic economics (buying individual products repeatedly therefore paying profit repeteadly vs. mass produced discounted parts bought in bulk therefore only paying for profit once) to system conflicts that in the long run might cost you more $. Second is the element of tech support. When the hardrive and DVD-ROM on your homebuilt fails you will have to contact each of those companies separately, each having their own policies. If the same thing happens to your Dell you will only have to make one phone call and it's taken care of. And everyone I'm sure knows the quality and reliability of Dell tech support. They have a reputaion of getting things done and done quickly. The third reason is rather futile but is still valid. If the whole system breaks down on you for some reason then you have someone to blame if you buy a Dell
. What will you do if your homebuilt chikes on you? Probably kick yourself in the ass for puttin gin all that work for nada. It's really a BS reason but I thought I'd sneak that in there
If I'm guessing right, I'm thinking that one of the reasons that you want to build your own is because you want the latest and greatest technology (fastest processor matched with lotsa RAM; a video card that has lotsa memory and a motherboard with twenty five slots). I would suggest not doing this because what's great today is becoming outdated as we speak. You are going to need to find the sweet spot in technology which is approximately the middle mark in current innovation. The sweet spot gives you the most bang for your buck in terms of being outdated because you are not paying a hefty premium for being one of the first to have it but you are saving yourself tons of money too by having current hardware. So let me see, right now the sweet spot would probably be 1GHZ system with 128 RAM and a 20 GB hardrive or higher and a 17 inch monitor (although those 19 inch flat screens are getting cheaper by the minute).
But like I said, gauge your needs first. You don't want to overpay for a powerful system whereby you're only going to use half of its technology. Instead put that money into something that you know for sure you'll use.
If you need more info let me know.
Its better to be on the ground wishing you were in the air than be in the air wishing you were on the ground. Fly safe!