Let me ask you several multiple choice questions in response to your question.
(1) At some point in the near future there will be a cutting-edge, must have game which will be exclusively: (a) DX9 or (b) DX10. (2) The biggest advances in APIs, providing both faster performance and superior sound and graphics, over the next year will be in: (a) DX9 or (b) DX10.
The answers are 1:b; and 2:b. Giving up 10 FPS with SLI right now is a pretty good trade off for being able to take advantage of all the coming improvements in my book.