Kris,
Get the Furman power conditioner, yes it's expensive compared to the cheapos out there but, it'll keep your power constant, clean the noise and if the power available goes too low, or overboard it will shut down. Your gear will be safe.
As for the ground loop it can be the old wiring or it can be your laptop's plug. My house down here is wired for industrial needs. Two 200 AMP Triphase circuit boards feed the house while a third 200 AMP Triphase circuit boards services the garden that's where my power distro hooks up. I have enough juice to throw one hell of a party. Everything is grounded properly. My Sony Vaio laptop provides great clean sound when plugged in (Regular socket with no ground) while my HP laptop does have the ground and it makes a ton of noise so I need to use a ground lift.
The venue should have an electrician check out the wiring to see if it has the needed capacity and it's done properly but other than that the ground noise may or may not happen.