The reasons why the cheap speakers sound as good:
Technology improved since you bought your CDT's; run-of-the-mill speakers improved significantly (listen to latests Philips splits).
Speaker sets are only better if installed to optimise the position of the loose speakers for the vehicle it is installed in.
The one exelent installer I know had to fit his very, very expensive smaller (loose speaker of the three-way set) of his own car smack bang in the middle of the other one (of different size and therefore other optimal range). Nothing wrong with it, all that counts is that the sound must sound real.
There are two different headunits in play here, and most probably different amplifiers (links to first point above too in a big way). These items make a huge difference to sound quality (and even the circuitry inside the head unit). A good 6 x 9, installed optimally is much
better that a good set/combination installed less optimally (old news, but very true).
What are you playing through the two systems? Music optimised for SQ?
Maybe your ears are not what they were used to be (hate me, its fine).
Maybe your old system is just that by now?
The combination of headunit, amp, speakers and location may make/create a sound spectrum that appeal much more to your ears (or put differently; make the type of music you like). Even the best splits/combination of speakers make very different sounds as each other.
I know I stated the obvious above (to the gurus) but did it with the sole purpose as to ensure that the (other) sound lovers out there know/realise that money is not the barrier to the love of quality sound, it is the quality of the time that you spend on your hobby that makes it such a fulfilling and generally interesting past-time.