Need Advice on making this sound better

Welcome to the forum. I think I may have directed you this way?

We all hear different, drive different vehicle and listen to different types of music. This means that every system is somewhat unique. What you are lacking right now is detail and depth in your music. This comes from assuming that the amp in the cd player is enough to power the system like your old Mach system did. In actuality, your new player will be struggling to reproduce 15watts of clean power. Take this a step at a time is the best thing to do.

As far as the speakers go, I prefer to listen to the speakers that I am buying. I have a well educated ear for speakers and can make recommendations for you to look at, but it is you who ultimately listen to them. If this is going to be a long term project, take it the step at a time. Each step you take will result in an improvement in tonal response.

I would send the one unopened set of speakers back and get yourself a 6.5" or 6x8" pointsource type speaker if you do not want to cut up the door panel to mount a separate tweeter. If you do not mind adding a separate tweeter, buy yourself some oversize 6.5" component speakers. You will need to make a abs mounting baffle to mount the mid onto that will in turn bolt to the factory mounting holes in the door.

Next add a amp. If you are not trying to blast yourself out of the vehicle, either buy a good 4 channel amplifier to power the front and sub (eventually) or use it to power the front and rears for now and expand to add a second amp when you add the sub. Powering the rear speakers off of the deck is a accepted practice that does a respectable job, it  is not however the way that I would do it long term.

The better bet here is to purchase a 5 channel amplifier that will run the entire system and use the cd player to it's full capabilities. Add the sub when the budget allows as you will more than likely be lookig for a highly specific sub and a custom box to house it.

Take the spec sheet and put it up to your ear and tell me how it sounds, for the most part a spec sheet is a colaboration of troublemakers looking for a place to set up camp. Your amp is not a monster by any means but it is 100% better than trying to rely on the tiny amplifier in the cd player. It will have crossovers to keep the nasty bottom end that distorts speakers at bay. If they are used then it is adviseable to use a small sub of some kind, an 8" or 10" is more than enough to adequately "round out" the natural sound that is beyond the capabilities of the main speakers. More power in the amp would have been nice but let's work with what you have for now.

As far as the speakers go, ensure that you do this. Sound deaden those big metal gongs that are called doors, this will drastically improve the tonal response in the mid bass region. Next, if you have a mounting location for a factory tweeter up high in the door (usually in the sail panel - the panel that covers the bolts that mount the side mirrors), you definitely want component speakers. Again the oversize 6.5" is the ones that you want. To make a mounting adaptor is easy. Take the factory speaker , place it face down on a piece of paper and trace it out. Next take the new mid and center it onto the same piece of paper over the area that you just traced the factory speaker onto. You will notice that it protrudes over the sides of the factory speaker line. Trace the new speaker over that area. Cut out the paper. It should resemble the factory 6x8"  with a couple of bulges out the center area. This can now be used as a pattern to trace onto 1/4"abs. If this is beyond you, have a shop that works with plexiglass etc. or a car audio shop build them up for you. Yes it is work but it is well worth it. We charge about $50.00 CDN for this.

As far as the speakers themself go, the #1 most important speakers in the vehicle are the front speakers. Pour some $ into these speakers.  My recommendations here are the German MB Quart (not the Chinese ones), Focal, Eclipse, Morel and then we can look at the middle of the road speakers like Alpine, Kicker, Pioneer etc. The difference in tonal response is huge, get good speakers. At present if you are after some great speakers, the Focal 165V2 or 165V1 (a little more price sensitive) would be the far superior way to go. A note here, most speakers like this are not available at www.TrailerParkTerry'sDiscountAudioEmporiumandFleaMarket.com but they are found at a specialty retailer, so a little detective work is necessary. If you need help finding these speakers in your area, there are a number of use that can point you in the right direction. The best bang for the buck comes the hard way. 99% of customers who take this route find out later that they bought the wrong equipment. Save the time and headaches and purchase the proper pair of speakers the first time.