Amp and preamp on same outlet?

There's no way to tell unless you try it. In your case, a good solution may be to plug the amp into the wall, and plug your preamp into a line conditioner that isolates the outlets. With power products, though, there's no telling what kind of results you get. If you call Cable Company, they can make recommendations and send you demo units to try first, before you buy. Its the best way to do it.

The first step is to be using a dedicated AC line. If not, don't plug into a line that shares use with high-draw items like appliances.
Get 2 20v dedicated lines, then you can follow ARCs advice; one line for amp and pre, next line for components.

The outlet is most likely on a 15 amp circuit that is rated for 1800 watts. If you total everything that is on that circuit it will not come close to that. If the breaker has not tripped then you should be fine. Enjoy your stuff and don't worry. Anything else is pure overkill!