AVR does not keep your PC running when there are blackouts. Only UPS is capable for that.
What AVR (Automatic Voltage Regulator) does, is stabilizing incoming voltage, protecting PC from brownouts (voltage drops) and surges (voltage increase).
Good quality, line-interactive, true/pure sine wave UPS, already has AVR in it and since it being an UPS, will also protect your PC against blackouts (power loss).
So, UPS is far better than just buying AVR alone.
Btw, what Watts the AVR is? Sure, it's 1000VA, but wattage wise, it is much less.