HeavyH,
I read your first post carefully, and it sounds to me like your best bet is to establish a relationship with a local, reputable PC shop that has been in business for many years. If I understand you correctly, you want them to be able to "Come out and fix it" if something goes wrong. That's where the local PC shop beats out the big hitters like Dell and HP, etc..
If that local shop is like the shops around here, they have their "stock" brands of components that they will use to build a system for you. But, if you request, they can probably custom order specific brand name parts. This is what I would do: take a generic list of components that you need in your system to them, and ask them to give you a detailed list of the system, complete with total price out the door. Then post that here so we can make sure you're getting quality brand name stuff. Once we sign off on it, then you can either give them the "go-ahead", or make changes as needed.
You want a gaming rig, so this means three things to focus on: CPU, RAM, Video card. Everything else is relatively unimportant. Spend the greater part of the money on those three items, and AH will run for many years for you.
I'm not going to suggest the absolute latest greatest in hardware, in order to keep the cost reasonable. That's why the more PC savvy folks here won't see me recommend a PCI-Express video card or motherboard. With that in mind, here's the generic list I'd bring to them, and see what they come back to you with:
CPU - Either Intel or AMD. Something around 3.0 Ghz. There's no point in arguing between Intel and AMD. They are both good. As Mrmidi pointed out, avoid any CPU with "Celeron" or "Sempron" in the name. They are lesser CPU's that are not suitable for gaming.
RAM - 1 GB is good, no less than that. Tell them you want good, name brand RAM, not some cheap no-name brand RAM. Kingston, Crucial, Corsair are just three names of good quality RAM. Also, make sure they know that you want at least one slot open for future upgradability, so that you can bump your RAM up to 2 Gigs in the future.
Video Card - 128 MB ATI Radeon 9800 Pro or 128 MB nVidia GeForce 6600GT. Both are great cards for the money right now. Not top of the line, but arguably "Best bang for the buck".
Motherboard - Anything from a name brand, reliable manufacturer like Asus, Abit, MSI, Gigabyte. Make sure it has at least 4 USB 2.0 ports, although 8 would be better. A good motherboard will have a decent built-in 6.1 or 5.1 surround sound card on it that is good enough for gaming. You could also spend $120 more and get that Sound Blaster Audigy 2 game card that MrMidi recommends, too. But for just gaming, a good motherboard will have a decent onboard sound card that would do the trick. Stay away from motherboards that advertise "AC97" sound card. That's not quality. Also, make sure the motherboard has an onboard 100MB ethernet card built in. That will prevent you from having to purchase an additional network card.
Hard Drive - Don't buy a huge, expensive hard drive if all you're going to do is play AH and a couple other games. Be frugal here, and the money you save on the HD can go toward a faster CPU. An 80 GB hard drive is plenty big for anything you'd need.
CD-ROM- Another area to be frugal in. This is a gaming rig. Put all the money into the CPU, RAM and Video card.
Modem - If you're on broadband, you won't need this. But if you live in the sticks, you'll need one. Something name brand is fine, like US Robotics.
Case/Power Supply - You don't have to spend a lot of money here, either, but you want to get a case that has at least one intake and one outtake fan in the case, besides the fans on the power supply. See if they can use a case and power supply from Antec. If they can, you know you will have a quality case/power supply. Power Supply should be at least 430w.
If you can get them to give you an itemized parts list of the components they are going to use, do so and post it hear for us to peruse. We can help you avoid any junk. In fact, don't be afraid to tell them that you want name brand, quality components....and that your internet gaming buddies will be checking their list to make sure they're using quality components.
Good luck! You should be able to get a decent gaming rig like this for $1000-1500.