Would an i3 530 allow the 5750 crossfire to breathe?

If you can afford the quad cores,then go for them,i5 750 would be a great choice,otherwise go for the i3 530 and OC it.
And 2 5750s won't perform like a HD 5850,they are slower than it.
2 5770s would perform like a 5850(even faster in some games)

If you really want a quad core I would well advice looking into AMD's budget chips.

AMD boards are dirt cheap and so are their CPU's.

An Athlon II X4 at 2.9 Ghz costs nearly nothing: $99.99

They are not the fastest quad cores but are one hell of a lot cheaper than intel competition, and certainly very capable of good gaming.

Then add a cheap 40$ board to that and done.

+1 to Maziar

Both i5-750 and 2 5770s are solid and best value for money.
If you insist i3-530, then overclock to performance like stock i5-750.

I live in canada so 2 5770s are around the same price as a 5850. I am considering getting the i5 750 as it is the best bang for your buck. What would be the best bang for your buck GPU(s)?

Why do you want 2 5750s (why not a single 5850?) Do you already have one 5750?
I don't recommend going the multi GPU route when you can do it with a single GPU.

Yeah, for an HTCP build especially you'll want a single GPU for less power/heat.

IMO stick with i3, OC it to max on stock volts (or as much as needed until you don't gain performance, then lower the volts if allowed) and get a 5850 (unless you already have a 5750).