It's not mandatory that anyone's system be surround if they prefer stereo, IMO. Surround doesn't necessarily sound real, but it usually sounds spectacular with respect to special effects. Car audio has traditionally been for best stereo image, low noise, smooth sound and tonal balance but surround has setup demands that are different. If you like stereo, go with stereo. Realistic ambiance is hard to achieve, even with 5.1, 6.1 or 7.1. Subwoofers are more difficult to "knit" to the main speakers, so if you get some good towers that can produce full range well, that may be best. If the woofers, mids and tweeters are time-aligned well, they'll sound best. It's best for the sound to come from the smallest area, rather than having the woofers in one place, mid-bass in another, mids and tweeters is other places. It's like having 6" 2-way speakers in a car with the tweeters at the top of the pillars and the mid-bass at the bottom of the door panel- it just doesn't sound right, regardless of which crossover is used and is touted as "tolerant of wider separation of the drivers". Phase cancellations occur and imaging suffers.
RE: "Sub- always", it depends on the music if a music system is the main goal but if special effects are a main factor, it's hard to get the impact without a sub. Sometimes, great bass (not in the lowest subwoofer range) is better than great subwoofer that's hard to mate with the main speakers in the crossover region. IMO.
