I need some help choosing a lipo... and some set up..

Hi everyone i am going to be getting lipo battery soon and i wanted to know if this is any good ProTek R/C LiPo Pack (5s1p, 18.5v, 4000mah, 20C, orNeu Energy LiPo Pack (4s1p, 14.8v, 5000mah, 25C, how much run time can I get in a kyosho mp7.5 with a novak BL kit and the HV 4.5... I know the esc can only do 14.8 volts and the Pro Tek battery has 18.5 so that is a nother question can i run a bec so i can use 18.5 volts..

So if i can use the pro tek with the novak motor and esc then that is what i will get... But if i can not then i will the get the Nue Energy and a MMM when they get the problem fixted.. And a Feigao motor not sure which one so it would be greatly appreciated if i could get some help...

So if i go with the nue energy and a Feigao motor and a RC monster motor mount, a RC monster batter tray, A mmm or maybe a mm and a bec. Does this set up sound good.. I will be on a extremely tight budget because i will be racing a mp777 this summer yes it is nitro but i am going to start going to big tracks and races so that is what i have to run so that i can run a 30 minute main or more...