I'm new to the scene but very interested and I've got some cash I'm open to investing in this potentially risky arena.  That said I'm wondering if you kind folks can help me out with the hardware selection.  From what I've read the HD 5970 does 802 Mhash/s, 2.3632 Mhash/J, 347 watts on ubuntu which makes me think a few of those would be a sound starting place in terms of power/efficiency/power use.

Budget: $2500 CAD or less  (I've skimmed the $1800 build thread but I figured the extra leeway might changes things a fair bit).

For reference electricity here is $0.12264 per kilowatt hour.  Ideally I'd like the thing to be reasonably profitable but again I recognize that both difficulty and bc values are subject to change.  At the current BC->CAD rate I'd need 125 coins just to break even on the hardware (assuming the full budget is used) which I gather would take a while.