alot of factors come into play. it strongly depends on you. I love music as well as movies so if I were in the same situation I would make due with the cheapest way possible(mixed and/or used speakers) until I could afford the system I actually wanted. If HT is a must right now I would go with a speaker package or try to buy voice matched speakers as most packages probably come with a subwoofer. U should be able to find a decent set for $500 to sound good with your sub. I say good because you most of the time get what you pay for. If your happy with a good sounding system than thats all that matters. Once again it strongly depends on you and the sound quality your trying to achieve. U can also try both scenario's to see what sounds the best at that $500 range. If you find 4 good speakers that sound good with your others than go that route. Or maybe the 6 cheap speakers paired with your center and sub will sound better. I say go out and experiment until you find the combo that makes YOU happy.