I'm having a difficult time understanding your Dad's motivation. Did he finance the car or something? His house, his rules?
Sorry if that's a little too personal a question to ask. Feel free to refrain from answering. In any case, if you're stuck with using only chambered mufflers, you could always try a Flowmaster 10-series or a Spintech Super Pro-Street 9000-series muffler. Those are pretty aggressive mufflers that sound good on catted exhaust systems. I would definitely recommend tailpipes as well. It won't sound as loud on the inside of the car, but it will definitely still be loud on the outside. That's the beauty of tailpipes.
Headers won't necessarily make your car louder. However, a good set of headers (equal-length or otherwise) would positively effect the exhaust note. I've found in my experience that headers with equal-length primaries tend to give the exhaust a more organized note. There was a huge difference on my '86 when I went from some cheap Dynomax mid-length headers to Hooker SuperComp long tubes with 30" primaries. I know you can't install long tubes, but the principle is the same as when dealing with shorties.