Best efficient Line Conditioner UNDER 1K

Richard Gray RGPC 400S, ($700) VansEvers Model 85, Unlimiter or Model 85 Reference ($650, $675 or $900)? Or something else? While the PS Audio 300 ($1195) might be a better solution, it's only 50% to 60% efficient (100 watts in, 50 to 60 watts out). The Richard Gray and VansEvers models are all probably over 95% since they have no active circuits. What has anybody else tried?

I live in an apartment in NYC where the current is unreliable and limited. I'm looking for something efficient to counter the sags and surges I experience whenever my neighbor's refrigerator goes on and off.