I hear you on the woody poop. Your choice of filtration in the Eheim 2217 is excellent.
The trouble is, how do you push all that heavy stuff toward the intake?
I usually add in something from ageofaquariums like an otto 800lph internal filter or even the 1200lph one. Because the poop is so big, I usually switch out the finer sponges out of the suction cups and add in coarser ones. I forget which brand they are but my lfs has them so they must be fairly easy for them to order in.
The internal filter as well as blowing the debris towards the canister intake also takes up some of the debris to its own filter cups. It is much easier to just snap off the filter cups and give them a rinse in water change water than it is to go unhooking all the canister hoses to clean it.
You can even add an internal filter each end but then you might end up with heat friction which is what I found in my 6ft tank and it heats the water too high in the summer time.
I did find a solution, I also add a wavemaker to blow the debris up to the filtering end.
Don't have heart failure, you don't need to get the expensive marine ones, guppys aquarium online and probably some on ebay have a cheaper version which works really well. I have endler guppies in the tank as well, and none of them have come to grief with the wavemaker so its safe enough.
Waterchange once a week is pretty standard with all plecos. They like the nice clean water and they not only poop in it, they pee too which you dont notice but you will in the yellow water that comes out during water changes.
If you don't like gravel vaccing, I wouldnt advise installing an under gravel filter. It is nice for a start to have the poops going somewhere else like in the gravel, but you do need to retreive it with a gravel vac. It doesn't just disappear into nothing and you will see in the front glass that a black line of debris is sinking under the gravel.
You are aware I suppose that a 4ft tank is no where near big enough for 3 adult L190's?
Try putting your tank details and preferred filtration into this fish stocking assessor.
http://www.aqadvisor.com/AqAdvisor.php
I added in your tank as a 48 x 18 x18" tank, if its a 48 x 24 x 24" tank, the result may read different, so have a bit of a play with it and see what tank you will need longterm to keep the 3 panaques.
Here are the results my search turned up:
Note: Royal Pleco needs driftwood.
Warning: Royal Pleco is not recommended for your tank - it may eventually outgrow your tank space, potentially reaching up to 15 inches.
Warning: Your selected species may eventually require 223% of your aquarium space. You may need to deal with territorial aggressions later on. Try removing some of (Panaque nigrolineatus) or get a larger tank.
Recommended temperature range: 22 - 26 C. [Display in Farenheit]
Recommended pH range: 5.5 - 7.8.
Recommended hardness range: 1 - 15 dH.