X-loc.....theres only one down:
When your signal source passes through another electronic device, you lose volatge. It maybe mi-nute, but any loss will affect the quality of the sound. The only way to really justify breaking the line to your amp for a source EQ is to make sure its of higher quality than your deck.
If you do use a EQ be sure to turn off the adjustments on your amp ( bass boost - etc etc ) this will only worsen the problem.
I would also reccomend using high grade RC jacks for this. Try to save as much voltage as possible. High grade cables don't "bleed" energy like the cheapies do. They still will, but not near as much.