Turnigy 250w 10a Reaktor Power Supply Question

All,

I purchased the Turnigy 250w Reaktor as a reliable charger for my HPA(airsoft) Nan-Tech 300mAh 7.4v batteries.  Upon receiving it, I realized that I need to purchase a power supply.  The 2 I am considering are linked below.  I am not a battery expert, nor do I care to be.  I just wanted the ability to not cook my batteries like the cheap lipo charger I had was doing.  The charger says 250w, so does that mean I need the bigger power supply, or will the 240w work for my needs? 

https://hobbyking.com/en_us/t240-power-supply.html

and

https://hobbyking.com/en_us/turnigy-reaktor-pro-350w-23a-power-supply-100-240v-ac.html

Thanks in advance