so if i were to purchase Avid 9900-52538-00 External Sound Box - USB - External, i only need to hook it into my laptop and it will playback the midis with higher quality sounds?
I do not think that will work, that is only a connection device, it does not look to be an actual sound card.
You'd need something like this http://www.buy.com/prod/startech-com-7-1-usb-audio-adapter-external-sound-card-external/211875924.html,
although I would not really recomend that one unless you can try it and return it if it's no good. This is a bit cheap for quality external audio.
this should have better quality http://www.buy.com/prod/creative-x-fi-70sb109500000-external-sound-box-usb-external/217451056.html
You may need both, the sound card to process the data, and the interface to connect it and get the input levels sorted out.