first off, congrats on starting and good luck. Its a great program, but you gotta stick with it. It will work, no doubt. Just hang in there.
As I mentioned above somewhere, I personally mixed in runs to varying degrees, esp when training for a race, so I got my cardio fix there. Plyo is a pretty intense cardio workout, and Cardio max isn't bad, but too short imo. Core Synergistics has a good mix of cardio and resistance, and is pretty tough. I am not a fan of the Kenpo workout, i don't think its intense enough, my HR typically doesn't get into the zone on that one. Its not cardio per se, but Ab Ripper always has me breathing pretty hard!
All things considered, I agree that the cardio could be better, but really, p90x isn't about the cardio the way Jillian's workouts are (love her 30 day shred btw, often will sub that in for, say, Kenpo).
I'm excited to try Insanity (hopefully next month) and anticipate eventually doing what texasteacher35 mentioned above, which is integrating the Insanity cardio into P90x.
I'll chime in here now, because I've posted here before. I am doing Insanity, I'm now in week 2 after restarting because I took a little time off, and I am LOVING it! Some of the reasons why I did Insanity instead of P90X were because of the cardio. It's truly insane on the level of cardio, and it ramps up way more into month two of the workout.
I don't want to violate any of the TOS here and seem like a huckster, but I've been so thrilled with doing the workouts that I've become a Team Beachbody coach. You can see my link in my signature, but it's
www.goofyfitnessdad.com.
I am reviewing the workouts and giving a lof of content, and if you want to get any of the merchandise, please please please go through my products page, and tell a friend about me.
That's all the shameless self promotion I'll do.
On the running topic from mmouseforpres, I previously ran as my only exercise, did that for years and years. It about killed me to commit to 60 days of Insanity, but I did it. I'm mixing in running with my Insanity workouts, some days I'm too tired at the end, but other days I can run a half mile or a mile just to keep it going. I started on a Sunday rather than a Monday, whic makes Wednesday my "cardio recovery" day. I was not impressed with that Insanity workout, so I run on that day. Also, because of when I started, Saturday is my off day from Insanity, so I run about 6 miles on Saturday. One thing I'm about to add to my blog is a schedule where I mix in the Jeff Galloway marathon/half marathon training with Insanity, and show where you could do a hybrid of Insanity, focusing on the running. This would get you some great exercises for your core, like you want.
Sorry if I'm rambling, but I'm just really hooked on Insanity.
Please forgive the shameless plug, but, as in my blog, I hope I'm giving away way more information than I'm trying to promote.