Why don't you just buy a really good card now and later, when you get the new computer, put it over into that new one.
In the vast majority of cases (at least over here in central Europe) you pay less money if you buy the components rather than a complete pre-build system anyway, even if you include the small fee for the shop to assemble it, if you don't want to or can't do that yourself.
Anyway... with my "old" GeForce 9800 GTX I could play through BP2 just fine (even back in the un-optimized and .12 days). That card generation and it's equals should be old enough to cost very little these days, if you really just want a stopgap solution for the moment. For the mentioned card I found prices between € 80,- and € 120,- (though I don't know how much that would be in Canadian Dollar) and I imagine the Radeon equivalents will cost roughly the same.
