Alright, thanks to GOG, I'm ready to take PC gaming more seriously, but I'm in severe need of a GPU upgrade.
My issue is, I've been out of the PC hardware loop for too long, and I no longer understand the numbering schemes ATI and Nvidia are using, and which products are comparable from either camp.
What I'm looking for is a basic GPU, I don't need 36x SLI with, $80,000 cards. I'm hoping to keep the price in the area of $150. As this machine is an OEM, I'll also need to upgrade the PSU, so suggestions are welcome in that department as well.
This is more of a trial thing, to see if I can really dig into PC gaming. if it goes well, I'll likely plan out a whole new build in the semi-near future.
My CPU should be sufficient for most anything I'd need to play, and if not, I don't need to run at max.

You haven't given us enough information to help. Give us the specs of your machine. And what kind of slots (PCI/AGP/PCIe) do you have available for the video card. There are lots of choices out there to fit any type of machine. So you need to be specific on what you have.

Sorry.
Athlon 64 X2 5000+
2GB DDR2 PC 5300
PCIe x16 slot for video.(just assumed this was the standard now.)
250 watt OEM PSU, which is why it'll need to be upgraded as well.
Edit: Also, I'm in Canada, so, shopping from newegg.com, etc, is a waste of time, as a $150 card would likely end up breaking $200 by a good stride by the time it gets here, due to the lovely folks at Canada Customs.
Typically the .ca versions are fine, as long as they ship from within Canada.

Get a regular GT8800 if you don't need top of the line stuff. They're very good cards and are also very cheap now. They don't draw as a much power as the heavy GTX 260+ stuff, but you'll definitely need to upgrade that PSU to at least a 500W+, probably a 650W to be safe.

I've been strongly considering an 8800 for a while now. Basically, I figure if I can run Crysis playably (30FPS, stable) on at least medium, I'm good.
Is there a significant difference between different versions of the 8800? Would I maybe be better off shelling out a little extra for a 9800? How do the ATI equivalents compare in terms of performance and price?

I have a GeForce 8800 GTS (G92) 512 model and a 550W PSU, and the power supply is working fine as far as I can tell. I've had it a year and haven't experienced any problems.
YMMV depending on what else you use that sucks up power though.
Depending on the resolution you run at, there is.

My current monitor is 1440x900, and I don't really see any need to change it.
Are there some brands that are better than others, be it through manufacture quality, or support offered? Are there any I should avoid?
As for the PSU, I know you get what you pay for, so, any suggestions on a manufacturer for that?

Off-topic: It looks like the quoting feature is working well now. :)
My PSU is a Rosewill, and I'm happy with it. My GPU is from eVGA and I've been happy with it. Their warranty is also top notch from what I hear, but I haven't had to rely on it yet. Hopefully not anytime in the near future either. ;)
I've heard some bad things about Diamond cards, but I think they handle ATI stuff. Specifically weak soldering, but perhaps that has been fixed. It's been a while since I read anything about that issue.

I too have a FX 8800 GTS - 640MB and 1920x1200.
I've had it for almost 2 years now and it runs wonderful on my machine with a 650W PSU.

Do you think I really need a 500+ watt PSU? http://www.newegg.ca/Product/Product.aspx?Item=N82E16817182159 This one seems tempting.

I've read cases where people used stock PSUs with my card and were fine. It really depends on the strain your system comes under. If you hit a point where your system is maxed out on some strenuous task, that PSU comes under a heavier load.
I didn't want to take a chance so I upgraded. I've read cases where you don't want to get too powerful a PSU as it will be less efficient and therefore waste more power, so that's something to consider.
I know a 550W PSU works for me, and my total Wattage draw is usually less than 300W (according to my UPS which also handles my xDSL modem and 19" CRT). So, I imagine I could probably get by with less.
Oh, you'll also want to make sure your PSU has the right power levels provided for your GPU connection(s). Mine uses two whereas some slimmer cards use 1. I don't recall the names of the connectors, nor the voltage requirements for each one, but the specific requirement is there.
Once you select your card, you can then select the right PSU to go with it.

I think nVidia's GeForce GTS 250 or AMD's Radeon HD 4850 would be the best buys within your price range. They're quite similar in both price and performance. They won't cost you much more than a 8800 or 9800 either.
Most cards are built from reference, so the biggest differences between manufacturers are in prices and stickers. I've only had good experiences with XFX, though...

That's what I was thinking, I recall reading that it's pretty rare for a machine to actually exceed 300w total power usage, and that 430w is 80+ certified, therefore, more efficient than most.
As mentioned, I don't really need a lot of room for upgrades after this, because if this experiment goes well, I'll be planning out a completely fresh build.
I am having trouble finding an 8800 for sale though, Seems the oldest I can find without getting into the "gimped" cards is 9x00. Of course, the wikipedia article mentioned earlier in the thread claims that the 9800 GT is a rebranded 8800 GT, so, I should be fine with that as well. My only concern then is, am I paying a premium for the box to have a 9 on it, rather than an 8?

Really? All the Nvidia 200 series cards I'm seeing are over $200. Ideally, I'd like to keep the PSU + GPU combo right around the $200 bar.

This would seem like a good deal, especially if you're into the Call of Duty series: http://www.newegg.ca/Product/Product.aspx?Item=N82E16814150365

Dude, use ncix.com, it's pretty much all I use. :)
Also I'd recommend the ATI HD 4770 over the 4850 or pretty much anything else..it has that new fangled 40nm technology~
Very powerful yet affordable.