If you can, get the '92. It has a slightly restyled bumper and trunklid. It also has 140 rated horsepower vs. the '91's 130. It's also a slightly newer car and has been through one less Canadian winter.
Yes, 4-5 grand sounds reasonable for a '91 EX-R, but a '92 will likely start a little higher than that. Hondas are generally good for 300,000+ km's.
If you like the styling of the '90-'91 cars better, don't let that 10 hp advantage swap you though. I've seen dyno charts for friends' cars showing a '92 F22A1 edging out a '93 F22A6, with similar mods.
When you get the car and want to start modding it, or you just want more help finding a good dealer or deal, head over to
http://www.torontoaccords.com/
Good luck!