The one coin per day part of your request is where things get tricky. You could easily get 3 used 5870 for about 200ish each on ebay which would net you about 1300Mh/s and still have room to get the board,cpu, mem, and psu. Even better if you have some of that stuff already. This will get you under 1 coin a day though.
With difficulty rising again, trying to get 1 coin a day is getting more expensive. Also don't forget about electricity to run you rig(s).
My personal opinion is that if your electricity rates are fairly high then you should go for the most efficient gpu hardware you can get, if not then get many cards as cheaply as you can.