I can't be sure of anything, but the fact that your motherboard died a week after you installed the new card instead of right away tells me that it's likely that it was just its time to die, and that you should be able to safely use the new card with the other motherboard.
Incidentally, though that GTS 450 is quite a bit more powerful than the 8800GT, it actually draws about 19 fewer watts at load.
"They should rename the team to the Washington Government Sucks. Put Obama on the helmet. Line the entire walls of the stadium with the actual text of the ACA.
Fix their home team score on the board to the debt clock, they can win every game 17,000,000,000,000 to 24. Losing team gets taxed by the IRS 100%, then droned."