The PorterPort is probably the least expensive choice in an outlet upgrade. It’s basically a cryoed Hubbel hospital grade outlet. Keep in mind that it’s made of brass (just like most other stock outlets are). The "cryo" and the additional current capability is good though. Brass conductors will have a very fast and clean sound, but they can sound sterile in some situations. For the price, it’s a modest upgrade to stock outlets.
I have not heard the Synergistic outlets, but I have been hesitant to spend money on these since Synergistic does not tell us what material they use (brass, copper, bronze, silver, etc.). It may be very good, as Dave has said.
Typically, gold plated terminations/conductors can slow down the sound somewhat - give a more laid back or lush style sound (while still keeping high frequency response). The rhodium plated will give you resolution and detail and punch, but the rhodium can reveal flaw/problems in your other parts of the part cord (i.e. receptacle, fuse, etc.). So, yes, careful matching is important, but the rhodium sound excellent when you match up properly. Silver plating does make a very fast and clean sound, but I have found silver to be somewhat artificial (the voices and sounds just do not ring naturally). This is my own personal opinion, many people like silver.
I have found recently that un-plated copper terminations/outlets will give a blare/ringing in the midrange, so I cannot recommend these at all.
