While many GBA games are ports of SNES games, there are still many good gba-exclusive titles (Golden Sun, and plenty of others).
Maybe you should check more recently, because for PSX, last I checked, there was only one good emulator, and it does support sound.
If you add sound, lower the frameskip for a smoother animation, the difference between the X30 and the 4155 will be more apparent.
