PCI-E is total junk for an AMD system as things stand right now. All it is, is a faster bus. However vid cards haven't even toped out AGP 4X let alone AGP8X and they sure as heck aint gona be toping out PCI-E. Its junk technology if your looking at video performance so don't wait for it. The only good thing about it will come from having tons of PCI cards in those mobo (motherboard) slots. Personally I will have only 1 at most so it makes absolutely no difference.
If you want a system that will last a while but your only on a value budget then I suggest waiting until socket 939 CPUs and motherboards arrive in early to late June. By then hopefully a budget CPU will have arrived for socket 939 which is what your going to have to get. The other CPUs are going to be fairly costly in comparison. Just make sure you get a very good mobo that will allow you to upgrade your CPU later on if need be. This is where mobo chipsets come in. nVidia has an outstanding nForce3 250GB chipset that pretty much blows every other chipset out of the water on both features and performance. I'm hoping that they will transfer this technology to socket 939 mobos because it would make the perfect mobo. We will have to wait and see but the best one of those right now is an ASUS mobo with that chipset.
RAM is a major consideration. You will spend a considerable ammount of your cash on RAM. Always go with Dual Channel RAM, especially with the socket 939 CPUs. Your only concern is either going with 512MB or 1024MB of RAM in either 2X256MB DIMs or 2X512MB DIMs. I can't quite suggest an exact RAM specification other than this because we don't know yet how current RAM will work with the new socket 939 CPUs. We will have to wait. I think its likely that we will be waiting until the end of June before benchmarks and good recomendations hit the Internet. Which is just as well since that will allow prices to settle down a bit.
For a video card you should get an ATI 9800Pro 128MB for best overall price/performance. Do not buy a 9800SE card because its junk.
Optical and Hard Drives are pretty much by preference. I don't know how much stuff you gona store on your computer so I can't recommend anything on this front. You just have to decide, but by the time you get to a hard drive you won't have much cash left so I suspect you will either have to go with a high performance 7200RPM drive or if you are not going to store anything major on your drive I suggest the WD Raptor 36GB 10,000RPM drive which will cost about the same as a high performance 250GB 7200RPM drive but the performance on the Raptor will be much higher.
Sound card will likely be a non issue. Assuming ASUS and nVidia stick with their current best chipset and include something like SoundStorm on the mobo you will not need a sound card at all. The onboard sound in this case will be virtually the same unless you have really good ears, plus it should support 6.1 sound.
Speakers are another question mark. Again this is perference. Wait until you find the right motherboard before deciding on speakers since if they don't include something like SoundStorm on the mobo you gona have to buy a sound card which will bite into your budget and will leave you even less for a sound system.
The case is not unimportant. Get a decent case and not some plastic toy. This will depend on your budget of course. Its hard to recommend anything in this area since its again perference and it depends greatly on your budget by the time you get to picking out a case.
The one thing you should never skimp on is a power supply. Get a good high quality PS from Enermax or a similarly good company. 350-430Watt PSU should be good enough. Getting a low quality PSU will result in system instability, damaged parts or total system failure. I see it every day at work where our IBM workstations are dropping like flies due to poor PSUs.
My new system won't be that dissimilar from yours, I even live in Canada so I know how hard it is to find good computer parts online or elsewhere. The only difference is that my budget is about double yours, which will be sunk into the CPU, video card, hard drive, and lots of high performance RAM.
Anyway this is also my first system. I have built many, including a major overhaul of my current rig but never built one for myself from scratch.
Its so exciting I can't hardly wait. =D
P.S. Edit: I forgot to mention why AMD. AMD is for gaming and it costs less. If you compare a whole Intel system to AMD your looking at a hefty price difference. Intel is better at number crunching and some applications but not games so it aint worth the price, especially when your on a budget.