I have 2xleadtek 6800gt's. for them to fit into my DFi i had to remove the plastic covering and one of the rear copper plates. I understand that the DFi has the same spacing as an MSI. I can email some pics if you want.
The cards will do it, although you might have to modify the cooling solution to make it happen.
You can either get some reference coolers, or simply modify the stock ones. Although in case you ever have to RMA one of the card's I'd suggest keeping at least one unmolested stock cooler around.
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