Sound system recconmendations

[NiftySVX]

So I've been fighting a horrible resonance in my svx since i put my aftermarket boston speakers in it back in 1999. I have since owned 2 lexus vehicles and really want to do something that will bring the sound up to a "premium" level. I don't need it to be loud, I just want full, powerful sound that will have a natural, balanced tone to it. I think this would be possible considering the speaker size and location offers a bit of flexibility. Are there any other audiophiles here that have found a good setup, without adding a sub or amplifiers? I know it's not possible to get anything that could even touch the Mark Levinson in the Lexus, but maybe something that could approach the JBL systems in Toyotas and still be less than $1000?