i want to record some songs on my computer. In my songs there are some parts
that have to be played clean. So i want to buy the boss ac-2 acoustic simulator
for better sounding. Is this DSP good or can you recommend another?

theres a difference between an acoustic sound and a clean sound. If you want an acoustic sound, then go ahead and buy that acoustic simulator, i'm pretty sure its good. But if you want a clean sound, then just get an amp with a pedal where you can turn the amp distortion on or off. Or hell, just get a distortion pedal and switch it off when not needed.

__________________