Cobra resonated exhaust and Y pipe

[Peldrigal]

So, I have installed a Cobra resonated exhaust, and I was quite surprised to discover that it was actually quieter than the admittedly old, rusted, and holed original exhaust.
I have heard that they come alive with HFC, but I am curious: is the stainless steel Y pipe something that is needed or will improve the sound, or is it something that I can skip if the original one is still in good condition?

[Coz@TORQEN]

The main change in sound will be from the cats and the backbox, most Y-Pipes on the market are exactly the same design as standard and will not have much effect on the sound.