What size APC battery backup do I need?

[advan]

Thanks, supersparks! Wasn't sure which should go down, the watts or the VA.

1. If I do have a powerful card (how do I classify if it's powerful or not? nVidia 8 series and up would be considered powerful?), which should go up, W, VA or both, and by how much?
2. Is computing for the UPS wattage requirement as simple as PSU+ Watts of lcd? I wish the APC site gave some numbers on my set up alongside its recommended products.
3. With my former UPS, I thought that when the UPS has been used actively (meaning, there was a power outage), when power comes back on and I'm done with work/PC's off, I'd leave the UPS plugged on to "recharge" so that for the next use, it won't be on low or drained level. I was told I shouldn't do this and that the UPS should only be working when the computer's using it?