I often wonder about this, how to balance the cardio with weights. The typical stuff you read is to keep cardio to a minimum to maximize your muscle gains and get big.
However when I look at MMA athletes and see how they train, I notice they look pretty impressive (eg GSP, Lesnar, Sonnen, Maynard, Mendes, Ellenberger etc). They're not BB comp level, but they're better looking than 95% of the guys on the forum, so it makes you think why not do the extra cardio, together with the weights and try and get that kind of physique.