I want to share this with ppl who are looking forward to replace their speakers while keeping the HU. Here's what happened:

I just finished installing the 5752i I bought off ebay. I still have the stock HU and rear speakers. Can't say I'm totally happy about the sound but can't complain too much consider the amount I spent ($35 + couple hours of work).

It sounds a lot cleaner now. In fact I find myself putting the fade towards the front so that the sound won't be "runined" by the rear speakers. But still not very clean and punchy enough. I guess the stock HU is the bottleneck here but I'm still debating whether I should get a new HU. Limited cash and I really want to get a B&M SS and an AEM intake. But that's another story.

Installation wise it went pretty smoothly. I had trouble aligning the speaker and door holes. I got it fit by putting in the screws at a slight angle and hopefully I didn't break anything.

 

I think the stock HU put out 25W/ch peak so the RMS is probably 10-12W. If the HU is capable of 25W RMS we won't have a problem!

The reasons I don't want to get a HU or Amp is because 1. money 2. thief 3. wife! So if I'm doing anything to the car it'll be a hidden mod. So the intake and short shifter are both ok!

I notice a bit of rattle from the left side today when playing it at higher volume. I'll might take it out again and put in a dynamat speaker kit. Might as well get a dremel tool to make the speaker mounting hole larger.