I haven't heard the SG2, but I own HK system. I do have a ton of experience with aftermarket audio(25 yrs), and I'll back up what Grimmy says, if you like features and functionality, less headache and great sound, get the HK. The diff between the two is 700 bucks. If you try to upgrade the sg2 to a full aftermarket system, you'll spend that 700 on just the LOC (if you get a JL Cleansweep). That doesn't include your amps, upgraded speakers, subwoofers, wire, labor. JL sells a 12 inch stealth sub that's 600 for just the sub and enclosure. That's without wire, or amp to drive it. If you were to get out of there under 3 grand, I would be HIGHLY surprised. And that doesn't even go into all the integration problems, especially if you get a new head unit( 1000 more). I have heard and built quite a few car systems, from boom trucks you can hear from 6 blocks away, to sound quality setups where you can hear a pin drop on the studio floor. The HK system is a GREAT stock system. I have no desire to change mine, and I am a stereo nut. Will it hold a candle to a dedicated SQ system? Yes, it is THAT good. I'd be willing to bet that you could even win some SQ competitions with it, or at least place well. And that's against systems costing 10 grand or more. If you get the HK, you wont miss the spare tire. You really need to audition the two systems to get an idea for yourself. Some people cant hear the difference or have different tastes, but IMHO, it is the BEST stock system I have heard, and I have heard a ton of them.