Adding a Cisco Gigabit Switch

Are you having a problem with noise? Have you narrowed it down to the streamer if you are? Couldn't be from something else? 

No issues with noise.   I have been reading About and discussing a re-clocking device with a friend who has the Wyred 4 Sound Femto re-clocker.   After reading a recommendation for the Cisco switch it was a less expensive way to get a re-clocker that offered potential NR and RC at the same time.

A network switch does not "reclock" the signal like you think.  It uses a "store and forward" data packet communication method (like sending letters through the mail on random days).  Most Cisco switches have built-in switching power supplies.  They are great and very reliable for normal computer networks, but aren't the best solution if you want something to reduce noise.

So if you want to try to shield noise from your cable router, buy a cheap switch like an Asus or anything from Best Buy.  Then buy a linear power supply like SBooster or a Teradak linear power supply from ebay/china (these are very good).

Like djones51 said, you may or may not be getting noise from network.

The Cat 5e cable is fine because you are not likely going to run anything faster than 100 Mbit anyways.  The Pro-Ject streamer is what clocks the music signals, and if you use USB to the DAC, the DAC has to re-clock the information into the right sampling rate anyways because USB uses different clock frequency.

I don't know that putting a switch in the middle is going to give you the best results.  I think you will get a lot more results from just upgrading your Pro-Ject streamer with a 18V linear power supply (like SBooster or Teradak/ebay).  Also, you should do the same with your DAC if it also uses a switching wal-wart power supply.