For $200 CDN I'd get one of the following (make sure to pay a lot of attention to the specific model numbers):
NVIDIA GeForce FX 5700 Ultra
NVIDIA GeForce FX 5900 XT
ATI Radeon 9600 XT
ATI Radeon 9500 Pro
The ATI Radeon X700 is the best choice above the aforementioned but it's not out in AGP format yet. If you wanted to wait, this would be the best choice. If you didn't want to wait, the cards listed above will do ya good for $200 CDN. I'll say that for a few dollars more you can get into some really powerful videocards. $230 CDN will break open a barrier that yields a huge performance gain with the Radeon 9800 Pro or the lesser Radeon 9700 Pro. Both of these cards can be bought for under $230 CDN and will be GREAT cards for their pricerange.
Like I said before, if ya wanna stay at $200 CDN, the cards I mentioned above are your best bet.
PS: You wanted a 256 MB videocard but I didn't list any. This is because the onboard memory on a videocard means precisely dick.
-Lasereth