I currently have my 4 Polk db coaxials in the stock locations connected directly to an Alpine CDA 9811 using the stock factory wiring. I have heard these speakers sounding better in another car using external amps and a very high end Sony HU.
1. What difference would powering the speakers on an external amp make in terms of sound quality?
Also I am on a limited budget so would it be a reasonable idea to use an 2 ch amp for the front and the HU internam amp for the rear speakers?
What relatively inexpensive brand/model of amp would you reccomend?
2. Right now my system really has no imaging to speak of. Adjusting the time correction can shift the balance of sound but it is still pretty diffuse sounding. I have a 1991 Integra with speakers in the doors in front and facing up behind the rear seats in back. Is there a cheap way to improve the imaging without extensive modifications?
forget sony. keep the alpine. an amplifier will give more power, which will give more warmth to midbass and lower midrange as well as improve things like SNR, distortion, damping, and head room, which in general are going to improve the transient response and performance of the speakers even at lower volumes. lok at a smaller 4 channel amp such as a Kicker kx600.4 that'd do the job nicely, and your head unit should offer front and rear RCA pre-outs for this. In fact I know the 9811 has 3 sets. you'll go from 26 watts x 4 to 50x4 and you'll see a huge difference. if you want to step up after that, look at adding a small powered sub like an infinity basslink to the system from the third (sub) pre-outs to fill in the missing low end response of the system. you'll be all set then.
oh, and for imaging, you can put separates up front. decent ones. put the midrange down in the door and have the tweeters mounted higher in the door, or in the A-pillars. I've done integras before, and that was the best way to set up the front stage.