Yes there would be a difference but would it be noticable I can't say.
CPU handles your logic
GPU handles your graphics
APU handles audio
Integrated Sound and Video are clearly not as good as their independant versions and do not hog system memory. Most GPUs will have 256 or 512 gddr3 memory if it's new today and the X-Fi processors if I remember correctly have 64 megs of memory.
This doesn't take up vital system memory but again does anyone trully need 64 megs of audio memory? The X-Fi Processors also re-sample music seemlessly using it's 24-bit crystalizer to make mp3s sound better than the origanal bloated CD files.
Will you hear a difference yes, will you see a differences in fps logically it helps but will you notice probably not.