Reply to Benefits of External Sound Card vs Laptop's Internal

So I'm just getting into DJing and have a Mixtrack, a good pair of headphones, and a cheap $5 sound card for monitoring/cueing. So far as I've just been practicing, I've used my Macbook Pro's headphone jack as the output (connected to speakers) and the cheap $5 USB sound card to monitor w/my headphones.

I'm about to purchase Traktor Pro 2 and noticed that if I buy the Traktor Audio 2 sound card I can get Traktor Pro 2.5 for free. (Traktor is now $89; the Audio 2 is $119, so I could essentially get the Audio 2 for $30 extra!).

My question is: Would my Macbook's internal sound card and 3.5mm headphone jack be enough to power larger speakers for future gigs? Is there a reason (besides headphone cueing since I already have that) that I should invest in the Traktor Audio 2?

Thanks!