If you are using a preset sound "that is perfect for what your doing" is there any reason to EQ the sound LPF or HPF, etc...  Is it removing anything sonically beyond the sound???

If it's truly "perfect", then no. However, any source that's destined to become one contribution to a complex mix needs to find its place in that mix. Two sources that individually are "perfect" may have overlapping frequencies that require one to yield to the other, which means applying equalization. So in the real world, most things do get EQ, no matter how great they sound in solo.

In some cases like this I would remove some low end just to make it manageable but in a lot of cases, I leave it.
Some times introducing EQ, LP or HP can hurt more than help. I have no problems with just leaving something I think sounds great.
Because I've been on the other end of the spectrum where I needled things to death using EQ soul searching for that perfect tone.
 
-More often than not that tone is found before processing.

In a sparse arrangements with not many tracks, you might get away with minimal EQ'ing, save for a bit of HPF to clean up the bottom end.
 
But as your project increases in density, there are bound to be instances of overlapping signals so you have to decide which sounds are the most important at any given point and carve out space in the less important tracks.

Appreciate the responses...

chuckebaby
 
-More often than not that tone is found before processing.

 
Word^

i high pass almost everything as a matter of course, to avoid the mud

bitflipper
If it's truly "perfect", then no. However, any source that's destined to become one contribution to a complex mix needs to find its place in that mix. Two sources that individually are "perfect" may have overlapping frequencies that require one to yield to the other, which means applying equalization. So in the real world, most things do get EQ, no matter how great they sound in solo.

What he said.  Every time you add a new sound, you change the EQ balance on everything else (even if it's very slight).