Mate, you seem informed - can u help me with my query here,
*www.digit.in/forum/power-supply-cabinets-mods/185115-apc-ups-replace-batteries-get-new-ups-5.html
System Wattage with GPU in FULL Stress = 339W from MSI GeForce GTX 560 Ti HAWK review - Setup | Power consumption
your ups can support. but considering its age, you can try with old battery. if it doesn't show overload, its ok. use the same.
if it shows overload - change ups to new one
battery low immediately - change battery and try. after changing battery it shows overload means, thats all, change ups. you lose money spent on new batteries.
i actually edited the post but it didn't update.