1997 Saturn sc 2 coupe wierd starting/shifting problem

ok for starters, this is a 1997 saturn sc2 coupe. i bought it about 2 months ago, and it shifts hard, but thats not my problem. upon buying it, it had an older kenwood stereo in it. i took it out and put my newer sony x-plode in and also put in my memphis 15 subwoofer. about a week or two after, i went to start it and it would continually turn over but not start. it wasnt giving power to the radio but had lights and power to the dash. so i got it towed to a shop and they told me the fuel pump went out. so i had them replace it for 400 dollars. so i was psyched to have my car back and drove it for about about a week and i went to start it and it did the same thing as before. so my dad had the mechanic come over and he said it was my radio and they messed with it and took it out and it started? like wtf. so i have no radio atm but if you put it in it will play fine and start fine for a while. anther thing, without the radio in it shifts smoother??. i took my car out to a stereo one shop and they told me its wired like they would do it and the radio wont cause the car not to start even if the wires were all twisted together and shorted out. they told me its more than likely my key cylinder is going bad or old or something like that and it would cost me about 150 to 200 dollars to replace. i was just wondering if that could be it and if it would fix all of my problems or not. just looking for a second opinion... plz help


ps i used a wiring harness in the stereo install and my amp and sub are wired straight from my battery and grounded in the trunk so the subs arent the problem