The world of after-market car audio is teaming with choices that rival and, in some cases, surpass the best sound systems offered by the automotive manufacturers. Looking for more music options but not interested in paying a monthly subscription? Check out the emerging world of HD Radio. HD expands the number of stations a single radio network has by piggybacking four or five different new stations onto a single signal. Think of it as hair extensions for radio.

With an HD receiver, you can tune in and capture unique formats, such as Clear Channel's Pride Channel, a station dedicated to the GLBT communities in Miami, West Palm Beach, Dallas-Ft. Worth, San Francisco, Hartford and Chicago. HD stations broadcast country, comedy, house, DJ, and the list goes on. HD receivers start around $150 and if you don't wish to replace your factory stereo, you can buy and HD tuner like the JVC KT-HDP1 that mounts on the dash or console and transmits through one of your existing stereo's FM channels.

The same aftermarket options exist for satellite radio, which gives a much broader entertainment choice and no pesky FCC regulations to limited what can and can't be said on air. SIRIUS and XM have announced plans to merge, so it really doesn't matter which one you choose, you'll soon have access to the best programming from both. Currently, SIRIUS has a channel dedicated to the GLBT community ( SIRIUS OUT Q ) , XM does not.

And no worries if you want SIRIUS but own a GM car with factory-installed XM satellite ready head unit. There are converter kits available on the SIRIUS site, as well as most audio shops, that permit you to make the switch. The SIR-GM1 kit fits most GM cars with satellite ready radio between 2003 and 2007. 2008 models like the new CTS are not covered, but chances are good there's a converter in the works for these cars as well. Not all GM cars are included, so be sure to check the SIRIUS site or call before you purchase a converter.

If money is no object, even a 1972 Ford Pinto can be decked out like the latest BMW or Audi luxury sedan. Pioneer's AVIC-Z2X retails for around $2,200 and includes a voice-activated DVD navigation system, Bluetooth wireless phone connectivity, an iPod adapter and a rearview camera that displays its image on the unit's seven-inch color screen. Alpine's IVA-W205 ( pictured ) , which retails for around $1,500, includes a removable GPS docking unit that can be used outside the vehicle. Most aftermarket GPS units include helpful points of interest that can quickly locate ATMs, gas stations, restaurants, phone numbers and more.

All of these systems can be found at your local big box stores such as Best Buy, which also have fairly competent installation shops. If, however, you're the do-it-yourself-type, online stores such as Crutchfield.com can provide you with all the tools necessary, including phone support should you discover you've bitten off more than you can chew.