No way the RE750 will hang with OEM tires, RE01R's, RE050A PP's, or Hankook RS2's in autoX. It's probably not well-suited for track duty either (judging from past experience with it's predecessor, the RE730, which chunked on my S13 at NHIS).

Going to 750's in 245 will lose you rear grip relative to going with RE01R's, RE050A PP's, or Hankook RS2's in 225 size (or RS2's in 245).

If you want a longer-wearing tire and don't mind losing some grip, the RE750's should be a great choice.

If you want better autoX performance and/or might do track days, stick with the Max Performance or Extreme Performance categories.