You would be better off taking Tyrosine instead of the phenylalanine since Phe is converted to Tyr in its own degradational pathway. Here's what the breakdown looks like:
Phenylalanine-->Tyrosine-->->->DOPA-->Dopamine-->Norepinephrine-->epinephrine.
As you can see, you could just substitute the Tyrosine in for the phe. Also, and i don't know how much Phe is supplement wise, but I know at places like Wal-Mart, Tyr can be easily obtained for about $4.00. Also, since Tyrosine is considered as a limiting amino acid in the body, it is only created from Phenylalanine when it is in low concentrations (semiessential aa). Therefore, the conversion of Phe-->Tyr would be even less efficient at producing catecholemines.
Tryptophan is a little more complicated in its pathways, but it can generate serotonin, niacin generation, and melatonin, etc. Basically, serotonin can be synthesized from Trp through decarbolylation.
Handsome Pete: I am no expert when it comes to SSRI's so if anyone out there sees that I am wrong, PLEASE correct my ass. Here is my answer though: If i am correct, Zoloft is used as a RE-uptake inhibitor for the blockage of serotonin (neurotransmitter)/norepinephrine. Therefore, you will have higher concentrations of these transmitters in the synapses of the nerve terminals, which is what I believe is the goal. I do not know if it will be overkill or how much or how little should be taken. In other words, since this is not really my "area", then I would suggest you ask someone like MS, par deus, Pat, macro, or cockdezl...they would probably be better suited for your answer on this subject of SSRI's.
MR. BMJ
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