Haha, i always want more too! Try this, again you will feel the burn in your lungs so good CV work, but it also challenges strength.
5 Dumbell Snatches per arm (starting with the non-dominant side)
5 Dumbell Swings per arm (starting with the non-dominant side)
10 Burpees.
You do this through 5 times, preferably with as little rest as possible (i would try going without rest). Normally you time how long it takes to complete and every time you try this routine you have to beat the previous time. if 15lbs was too light try 20lbs or 25lbs for this.
This routine was made by Ross Enimait and is called the Magic 50. I have done it a few times and it takes me 10 minutes just to psyche myself up to doing it. It is a really killer. You should love it! haha.
Sean