to answer the initial question: yes, it is.
let's say you only get 2x5850 (not 5870s) for $800,
2 5850s get around 700MHash/s and the rig will need ~375W (probably less, but let's just be sure),
at (very expensive) $0.3 per kW/h you'll pay $2.7 per day
at current difficulty the expected average output is 2.88BTC per day,
at current market rates (of roughly $6.5) that's $18.72 per day.
$18.72 - $2.7 == $16.02 per day
16 / 800 == 2% ROI per day
show me an investment opportunity that pays you 2% per day and i'll join it.
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at current difficulty rates.
The OP admitted that the rig won't be up and running for another 1.5 weeks, at which point the bitcoin system will already be into the next difficulty. Therefore, none of your numbers apply to anything the OP will see.
Some times I can't tell if people forget about the rising difficulty, or just choose to ignore it because the numbers are so much better if you do. Thanks to the members here who keep pointing this out. Note that most of the projections here that take rising difficulty into account have the OP
breaking even at some time in the future (2-3 months), at which point the difficulty will be so high that income will be a trickle. The only profit you're likely to see is from selling your hardware after the fact, but remember that plenty of other people will be eager to unload their ATI cards by then. That's a far cry from all of the claims that mining is 'very profitable' still.