Generally, there is no need to isolate or filter outlets. Most quality devices have sufficient filtration in their own power supplies to clean off any noise on the incoming AC.
The only time I've ever has ground-loop problems was between computers and radios in weak-signal radio contests. We isolated the computers by switching to laptops and that addressed that issue. But we were using radio receivers with noise floors over 130 dB down from peak receiver saturation--nothing that would ever be encountered in audio. And we were running equipment on generators, which do not produce the sorts of power integrity that we get from the power company.
Very few so-called isolators actually isolate, because code requires them to tie the safety ground across all receptacles. This is true even for transformer isolators like the Tripp-Lite medical-equipment isolators. The point of those is to filter out high levels of environmental radio frequencies.
As for surge protection, I do a LOT of that in my home, because we've had real problems with surges and outages taking things out. I have also installed panel surge protectors in my power panels--these probably would meet the needs for surge protection for most people without further protection.
Note that most commercial power isn't that clean. When I look at our power on a scope, the sine wave is noticeably distorted--there is a flat spot on the downslope. I would guess that distortion (compared to a 60-Hz sine wave) is probably well over 1%, and maybe as high as 10%. The Tripp-Lite "isolation" transformer does absolutely nothing to improve that, but it doesn't matter--that's why equipment power supplies have filter capacitors.
Rick "code allows a lifted ground only for equipment in an insulated case" Denney