Can you get decent bass without a SUB?
 

If you got solid aftermarket 6 1/2 speakers, powered by a solid aftermarket HU, can you get decent bass? Not hard hitting like you would get with a sub, but bass that is noticeably better than stock...

simple answer? no

Is an amp powering the speakers the missing link? Or is it a sub & amp combo?

missing link is a 6 1/2 that can push some bass.

You may be able to adapt 6x9s, since thats what the touring uses, and if you could do that, you may be able to do ok. I had some boston 6x9s in an old saab I had and they put out decent bass with the stock headunit.

there's an old saying in cars: "there's no replacement for displacement". speakers displace air to make sound. the larger the driver (speaker) the lower it can create frequencies. by this account there's no way you can replace a good 10" sub with a 6.5" speaker, it just doesn't have enough surface area. now, you can put an amp in and put in a set of 6.5" components and have a nice sounding system, but you will never mistake it for having a good legit sub.

you absolutely can. the key is properly deadening your door and sealing it up, almost making it act like an enclosure, It obviously wont extend as low as a subwoofer but you can get a serious amount of output. Theres alsothe option of using an 8" midwoofer and trimming the sheet metal on the door. You are however going to need to feed a solid set of mids a good amount of power.

by the time you add one 8" sub in each door, you are better off (in both cost and added weight) just getting a 10 or 12" sub to go behind the seat. i have an 8" sub in my truck and it sounds great but sometimes i wish it was a 10 or 12"

I've done some high end Focals (K2P's)with a good amount of power that had a lot of mid bass, for most this would have been good enough, but for the money spent a good ($200-300) 6.5 and sub with an amp would have been the cheaper way to go.

Does the sub have to take up space in the trunk? Or can it go somewhere else in this car?

if you can live without a spare...

If you don't need/want a lot of bass you can hide a pair of 8's and a amp in more then a few places that are dead space with no problem.

Depends on how much DIY you are up for. I made a fiberglass enclosure, using my spare tire as the mold. 10 inch flat sub driver. No trunk space (or spare tire) sacrificed. I have not powered it up yet, though. Still slogging thru the install.

I have done serious sound deadening in the doors and installed Alpine 6.5's and Pioneer HU. It definitely sounds better, the bass is tight, controlled, not boomy and indistinct like with the stock setup. But I feel the sub is still needed. If the spare tire sub does not satisfy my needs (I am not listing to hip-hop or interested in setting off alarms in cars as I pass) then I will build an enclosure in the empty space where the crash data recorder (and Bose amp for those with Bose systems) reside. Likely one of the spaces 90 ST was referring to...

and I put a bazooka bass tube in the space under the carpet right behind the strut bar. Its a 6.5", but its designed as a sub with some sound chambering and has a 250w amp and puts out nice bass.

As Mike mentioned above, there is space there, for a Bazooka, or a couple 8" and a amp. I have 2 bigger amps in that spot.

To update my sub info: works perfectly for what I want. Spare tire enclosure, 10 inch flat driver, Polk 300w amp. Only problem is the 'Z-logo' carpet 'rattles' against the driver grille. Hold it up and rattle is gone. Swapped in the cheapo standard carpet, and it sounds great. Way more bottom end than I need.