Although I'm on another Anti-Depressant, I certainly notices a positive effect from Amitriptaline that outweigh the bad effects.
It is very weird to be mixing two different antidepressants. Depending on what your other antidepressant is, it could be dangerous. Were your two medications prescribed by the same doctor, and if not, have the two doctors talked to each other? A very simplistic view is that some antidepressants cause the body to make more serotonin, and others prevent the body from destroying serotonin as quickly. Doing one is fine, but doing both at the same time can lead to serotonin syndrome.
Amitriptyline does have higher risk from overdose than SSRIs, but has much gentler withdrawal symptoms.
I find the ZoMorph blocked me up quite a bit, Fibrogel works well in this case.
Serotonin syndrome can be an issue with all kinds of things (most people aren't warned about being on a SSRI and having cough syrup for example), but is not very common in practice, and because it coincides with a change/increase in medication, often sorted out quickly, even if it's characterized as a "side effect" or "tolerability" problem and not actually recognized for what it is.