Hands down, components. Now, with good quality equipment like you have, namely the Excelon deck and amp, I really think you would appreciate the dramatic difference in sound quality with component speakers. One of the biggest differences you'll hear, is a much improved midrange/midbass section, since you will have a sealed separate mid woofer, rather than a woofer with a hole in the center for the tweet. The solid woofer will give you MUCH better midbass. Now, almost every time I tell someone about midbass, they tell me they 'already have a sub'. Midbass is the portion of music from about 80hz to roughly 300hz that most systems lack, either by inferior coaxial speakers, incorrect Xover settings, or by overbearing subs drowning that portion out. A proper sound system, will have a strong midrange/midbass portion, that blends into the sub, depending on where the components are high passed, and where the sub is low passed. The majority of systems I hear is all treble and bass, but when you add components, and proper tuning, the sound quality will improve dramatically. Regardless of RMS power handling, the components will sound much better. The external Xover is much better than a built in coaxial Xover, and it will much better route the appropriate frequencies to the right driver.
Now, there are a couple of other things I should point out to make the components sound great. One recommendation would be to place the separate tweeter as close to the woofer as possible. Now, that can be debated, depending on many external factors, but generally, you want the woofer and the tweet close together, so that they reach your ear at the same time. Many people will put the woofer low in the door, and have a tweet up in the dash or A pillar, and the result is that the tweet reaches your ear much faster, and the system may be appear to be 'bright' sounding, or just uneven. I've worked on a few towncars, but cant recall if a 97' has a factory tweeter location. My vehicle did not, and I installed the woofer in the factory location, and then drilled a small hole in my kick panel and mounted the tweeter there. The woofer and mid are about 8" inches apart, and even though the tweet is lower, with proper positioning and a little time alignment, they sound like they are side by side, and right in front of me, rather than low in the door.
My other recommendion is sound deadening. In order to make that midbass shine, and also to eliminate rattles and road noise, a layer or two of Dynamat in the door will help tremendously. There are many brands of deadening, but I like dynamat best. I used two layers on the outermost section of the inner door, and then covered the inner door portion completely, covering all the little holes in the door frame, and basically almost creating an enclosure for that woofer. I went from Infinity Kappa coaxials front and rear, to just JL components in the front, with no back speakers at all, and the sound quality in my opinion is ten times better. With excellent components up front, sound deadening in the door, and a powerful 4 channel amp, there honestly is no need for back speakers, especially in a vehicle like a towncar, where the back speakers dont face anywhere near the drivers listening postition.
I could be wrong, but I though that Towncars had 5x7/6x8 speakers in the door and not 6.5"s. If thats the case, you can buy 6x8 to 6x5 adapters, that will allow you to install the mids in the door without any other modification. I dont recall any towncar having 6.5" stock.
There are many good components out there, and even though your whole system is Excelon, which is good, dont let that keep you in a box in terms of future audio purchases. In the $200 price point though, the Excelons are pretty good, as is the Alpine Type Rs. I'm not sure what level you are trying to take this system to, but for double that price, you can look into high end components like Morel, Seas, Rainbow, Hertz, Focal, Boston etc. I was building an all JL system, and made the mistake of just assuming the JL components were going to be as amazing as my JL subs, but that wasnt the case, and I recently got a pair of Hertz from Italy that are MUCH better, so all I'm saying is to keep your mind open to other brands as well.
Sorry this was so long, but I really wanted to explain the benefits of components, rather than just saying 'components are better'. People need to explain 'why'...
Car Audio fanatic