A. The pawn shops aren't going to pay you squat for your 6x9s, if they'll even take them.
B. What funds do you have currently?
C. What's the story on the receiver your parents have, can you use it?
D. Have you talked to your friend about the other receiver yet?
E. I'm almost certain once you get a pair of decent speakers, even ones like those Daytons, you'll wonder how you could ever stand listening to the Sony speakers you have now. Those Sony cabinets appear to be made from particle board, and very thin particle board with paper drivers with crome plastic dust caps. Believe me, it doesn't get any cheaper than that.
Please understand, I'm not trying to knock what you have. I'm trying to educate you and get you off on the right foot. These HTIAB (home theater in a box systems) that you're looking at from Venturer, Curtis Mathes, Apex, and whatever else generic name you can find, are absolutely garbage. They're unreliable, wimpy, and their only design parameter is to look as appealing as possible without costing the manufacturer a lot of money to build and distribute. Those that haven't had a quality system may not recognize they sound bad, but they do. I used to think a boombox sounded good, but I don't have one anymore and won't buy one because they sound like crap.