if you have $2500 to invest on mining, get an asic rig. your best bet right now is to buy chips from zefir and then get the rig from burnin.
And then what ? For $2500 you have less power than the 1000 main miners on any pool which means it will take ages to get proper ROI. Spend $25000 (or more) or buy BTC rather than mine them ;-)