Need Better Sound.
I would definitely buy a power amplifier and new speakers. Check the Crutchfield.com site for equipment and technical information. If your budget allows, a new head unit would also be nice. You don't have to buy the top-of- the-line equipment to get great sound. Suggest that you determine what your budget will be, and search for equipment within your budget. Most of the items can be install by you on a Saturday afternoon. Read some of the post on this site, regarding how to install a amplifier and speakers. There are also videos on you-tube.com that show you how to wire your amp and speakers. Look for posts and videos that are specific to your vehicle. If you are not comfortable with doing it yourself, contact Best Buy and some of your local auto sound shops for estimates. Best Buy will let you bring your own equipment, for them to install.
I initially asked Best Buy and some local auto sound shop for estimate; but decided to do it myself after I found out what they charged and how easy it was. Kudos to the folks on this site who posted instructions and photos. I install an amplifier and 4 - 3-way Pioneer Speakers. Later, I added 2 more amps, 2 sub woofers, and 4 more pioneer speakers. I went a little overboard, but I install cut-off switches for 2 of the amps for times when I don't feel the need for extra sound.
Good luck, and good listening.
2006 GT, Strut Tower Brace, Gas Hood Struts, FR Intake Plenum cover, Metal Fuse Box cover, Moroso brake reservoir cover, Rear shock tower brace, Front Bumper Lip Spoiler, JVC DVD Head unit w/ back-up camera, satellite Radio and USB input, 2 - 12" sub-woofers, 4 - 6"x8" speakers, 2 - 6.5" speakers to replace the door subs, 3 amplifiers, LED lights under the hood and in the trunk, chrome e-handle on parking brake handle, chrome cup holder trim, and trunk lid cover with running pony emblem.