Reply to Do I Require A Soundcard?

So i've currently been producing for about 2 years and I've been mixing on a sony stereo system. The speakers are ok and they seem to translate well when i listen to my mixes on other speakers or headphones. Regardless, i soon want to get a pair of studio monitors. However, i hear from many people that i need a soundcard to get the most of my productions, but i hardly use any actual synths or actual hardware, everything i do is pretty much VST and MIDI. So do i need soundcard despite the fact that i dont use hardware? What exactly do I need it for?