I'm a mechanical engineer, with out serious cutting, there is NO WAY to get an IDQ6 or a CX6 (same basket same magnet - I've owned both) into the doors of a 00 Si.....Check your years again, check the doors again, and you will find that I'm right. I'm not trying to get in a pissing contest with you, it's my job to think outside of the box...it can not be done.
I don't doubt that you have tried. But seeing that I've builded, designed and sold car audio systems for going on 5 years I have a clue about what I'm talking about. In fact I personally know the guy that ownes ID a Mr. Eric Stevens, very nice guy I might add. I've talked with him before about products and installs. In fact I was the guy at the shop I work at that was trying to get ID in there. So look I've been around the car audio a lot more then you I'm willing to bet. I've seen just about everything done and I know what can be done. I know how big the magnet is on the speaker in question. There is not a 6 1/2 on the market with a magnet do big to fit in that opening, because there is no need for a 6 1/2 with have big of a magnet. Now your an engineer you should know that, if you don't would you want someone with an engineering degree to tell you why there is no need for that? I'll be happy to, I mean if you don't know how a speaker works I'll be happy to break that down for you, Mr. Engineer. Now just because you are an engineer don't try to tell me I can't do something that I've done personally. You know I started out just trying to help you out but if you say it can't be done hey it can't be done, right? You know I've never gone to school to be an engineer before but do they teach you how to use a Drimmel tool there? If they didn't go take a class at Home Depot about it.
Don't ever tell someone thats been in car audio that something can't be done when I already pointed out that it can and I've done it.
Also get your car years right all 96-00 Civics have the same doors.