Being a sophomore myself, I sympathized with your post and decided to respond.
I study Tomiki Aikido at a local YMCA. From what I have seen and practiced there, I don't think you'll be able to simply grab someone, apply some pressure, and have them begging for mercy. You will, however, be able to move your butt off the line of attack, redirect their momentum, usually throw them, and THEN be able to apply pressure in such a way as to have them begging for mercy.
Also, I don't think there are any actual 'tournaments,' wherein two aikidoka are put in a designated area and told to try and throw each other. There are certain sport-like activities, where one aikidoka holds a fake tanto and tries to stab the other, who tries to keep that from happening for a certain amount of time (In tomiki style at least). I'm pretty sure that in most other styles of aikido, there are no competitions of any sort. I realize you didn't want to enter any tournaments anyways, but just thought I'd mention it.
Also, certain styles of aikido are more oriented toward psychology and character building, and others are more oriented toward self defense. Regardless of this, you will be able to achieve what you said was your ultimate goal, to be able to defend yourself when people feel they can walk all over you, no matter what style you choose.
I would just like to note that you should keep in mind that it may take you awhile before your aikido becomes 'combat effective.' Some people are faster learners than others, but it took me at least two months before I could actually execute a throw in such a way as to REALLY move uke with my body weight, and I am only just now beginning to perform what techniques I know fluidly. However, being able to overcome the desire for instant results is part of the psychology/character building that was mentioned earlier. It is extremely beneficial to keep this attitude while training.
Finally, I do not know of any resources with info on other martial arts (you only wanted those if aikido wasn't right for you anyways, but...)
aikidofaq.com is filled with information on the origin, development, and principles of aikido, among other things. I'm sure you would enjoy stopping by it. Not to mention the several articles here at aikiweb =P.
Whatever your decisions, I wish you the best of luck.