Jeep Cherokee 1995 cuts off?

[Tristan]

I have a 1995 Jeep Cherokee. I have had it for almost 5 years now. Never had any major problems with it. When I first got it I put a system in it. Two tens 500 watt amp. I upgraded it to Rockford fosgate 10's and the Rockford amp. I was driving down the highway at about 70mph and my jeep died everything but the radio and sub-woofers. It had done this once or twice before only on highways never on roads, but it never died completely it would always rev back up and keep going. So I had it towed back to my house. The next day it started up fine. Sounded like it wasn't getting enough fuel but eventually after getting warm it ran fine. I took it to the shop they said it was not the fuel pump and couldn't determine what the problem was and could not recreate the problem. Since this has happened a little while before this my speakers started humming was I accelerated in the jeep and sometimes the subs would cut off but cut back on minutes after or sometimes just seconds. I haven't changed the sub's setup in the five years I have had it. Any ideas what could be going bad or happening with my jeep?