The SVD is regulated and does not require much from the battery, under 10 amps. I would use anything other than a battery with the word fire in it's name. Balance the cost/mah and get the battery you want.
With the mech you need to make a decision. How low will you go on the resistance? You DO have an ohm meter to check, don't you?
At .6 ohms you are only drawing 7 amps and just about any current battery, again stay away from the fires, will work. If you plan on going under .6 then the battery requires more thought.
There is nothing wrong with the Sonys. They are fine batteries but you pay a premium, cost and mah, for a battery that will produce 30 amps to put in a device, the SVD, that will never draw over 10.