in all honesty, it would be tough to get 5 decent speakers, a sub, and a decent receiver for $475. it sounds like you really dislike the sound of the onkyo speakers. if i were you, i'd return it, get a refurbished onkyo 503 receiver for about $190 from shoponkyo, and spend the rest of your money ($285) on a pair of good bookshelf speakers and a good entry level sub. it will only be a 2.1 system for now, but you can add a center speaker and then another pair of surrounds as your budget allows -- this will only cost you about another $250. this requires patience, though.
your other option is do what i did. i started selling off the 780 in pieces via craigslist/ebay, and made made most of the money i spent on new speakers back. in fact, i ended up getting more for that HTIB than i originally spent on it. this required me to buy my new speakers up front, then pay off the CC as i sold the onkyo pieces. not an ideal situation, but it worked out in the end.