Squeak makes a good point... installation quality, tunning, and speaker placement is number one.
For the most part, more amplifier power is what makes a system louder and more dynamic... if the speakers can take it.
Other things you could try would be a surround sound system.
- or more power + speakers/ a speaker system that will handle more power. Three-way systems can handle up to twice the power without compression, generally. (If the speaker can't handle the power and suffers power compression, it gets less efficient the more you turn up the volume... in that case, you need speakers that can handle more power)
If you have to stay with a two-way component set, Diamond D9 might be an option... but you may need to put a more powerful comp amp on them than you have now to get any worthwhile difference.