savage x conversion battery questions??

[ratpower396]

I know about lipos I have been considering them for quite some time but the problem is..
2 batteries = $40
1 charger = $100
1 esc to handle lipos $150
total= near $300
The setup I have is paid for & woking just looking to get alittle better run time out of it..
The esc is rated 100 amp & the mamba monster is 120 amp is that enough to justify a new esc??