I'd do all the comparative analysis in the world before making that jump. Also, I feel like speakers can swallow up some of the amplifier differences. In other words, differences between amps would be less apparent on crappier speakers. You want to be confident that your speaker will allow the upgrade to shine. I think there are amps that can operate as an A class and also as an A/B class...probably worth looking at if you're going the expensive amp route.
Hell's Racers by The Dave Meyers Effect. This is an old surf guitar track that isn't necessarily a SQ track but the race cars in the very short beginning of the track image outside of the vehicle to the left and right, and some of the guitar riffs are outside, too.
Also the old classic, "Tequila" by The Challengers...hand claps and shouts/howls that are outside the vehicle.
And these are a few tracks that I think Andy Wehmeyer recommended in another thread...
The Pink Panther track from the older IASCA disc has a Triangle strike that will image outside of the physical boundaries of the vehicle.
And the track from the EMMA competition disc where there is a guy that walks from side to side across the stage.
Mark Knopfler - Boom, Like That (a song about fast food, LOL)
There is a guitar riff that will image outside the vehicle. It's short but sweet.
'Moments in love" by the art of noise. its got a wide range of sounds, excellent image placement and tonnes of depth and width. In my car the xylophone on the far left actually comes from outside my drivers window and you can even hear the notes move forward and backwards as they are played. This is the version you want to get: Art of Noise: Moments In Love [Quiet Storm] - YouTube
The Final Cut, and Waters' "The Pros and Cons of Hitchhiking", were recorded with Holophonics (comparable to binaural recording) , intended to perform best with headphones. Possibly why a good car system reproduces the effect so well.
Waters later used Q Sound on "Amused to Death" with even better effect.
Needless to say my CD collection has grown