1. Do I absolutely need an amp and/or a subwoofer?
-absolutely? no. generally? yes!
And if you do suggest an amp, where can I put it?
-either under the seats or in the trunk. i prefer in the trunk.
Can i get one to fit where the factory one is?
-probably not, because of cooling issues. although blaupunkt's class t amps could work there.
Same thing with the sub...can I get anything small, to maybe fit under a seat
-no... but you can replace your glovebox with one. dbzjr has one for sale.
or a small enclosure in the sidewall of the trunk?
-much better way to go.
That Infinity basslink sub looked promising and there's a couple good deals on them on ebay.
-they are easy to install, but not as good of performance as you can get for the money.
2. Do all the components of the system have to be from the same manufacturer? I'm all over the place with brands so far.
-not at all.
3. So far, the components that I'm set on getting are a better deal on the net than in stores, but I'm not sure if I trust myself to try and install all of this stuff since I've never done it before but money is a concern and I don't know anyone who can do it for me.....anyone know any reputable installers in the nj/nj area? From lookin on here, it seems like Best Buy/Circuit City is like dealing with the devil LOL....I liked the people at 6th Avenue Electronics, but I'm still not sure and I don't want to end up with a headache.
-do it yourself! it won't take that long, and then once you do it, you'll know how to change it later (and you'll probably want to if you get the bug)
4. At first I was pretty much set on dropping in 2 sets of 5 x7 / 6 x 8 speakers but a shop i went to offered to make templates to set in 5.25 round speakers which opens up a whole new bag of speaker choices. What are the pros and cons to doing this? How will it affect the sound?
-generally, there are better quality speaker sets to be found in the 5.25" size range, as opposed to the oval ones. but there are good oval speakers out there (like boston acoustics). either way, the most important thing is getting a good quality speaker, and putting an amp on them.
5. Can anyone recommend a decent headunit and speakers, subs and amps? What should I be looking for when it comes to subs and amps? As far as head units, I'm pretty much decided on a Blaupunkt head unit because their specs seem good and I like the face layout and Crutchfield gives them good reviews...does anyone have any experience with them? I like the new panasonic head units as well, but I'm not sure about those either.
-this is way too vague of a question! i reccomend you do as much research as you can before you buy though. do searches here and at car audio forums, or at least come up with a budget. then someone will generally have an idea of what to point you towards.
Thanks in advance for any help

-np!