Yeah, the cheap batteries are not going to give you the full performance that your vehicle is capable of. Would you fill a performance car's tank up with discount 87 octane gas? Maybe if all you want is to get from here to there, but your not doing the car justice.
My experience with those cheap batteries was that they stopped taking a charge after a few months due to a cell in the pack going bad. Unfortunately I bought 4 of the darn things. In less than 6 months, none of them worked anymore. I have good batteries that are going on 4 years now and still work. Most of my batteries are between 1 and 3 years old. One is even a Duratrax matched 1900 that won't quit. If you are happy with it for now, thats fine, but I would say to not buy any more of those and save up for good ones.