Sound System Updates - looking for suggestions please!

[bdisney3]

I have a 2009 SANTE 210. Has the original Clarion CMD5 with wired Remote at helm. PO did lots of upgrades - all 6 in-boats replaced with with Rockford Fosgate 6.5" Component M262's,1 set Roswell 7.0 Airborne HLCD tower speakers, 1 set Roswell Unison Pro 6.5" Component Tower Speakers (in-boats and tower speakers driven by two Rockford 4ch T600-4ad amps (600 Watt RMS ea)), four 10" Rockford M210S4 subs driven by a Rockford T1000-1bd mono amp (1000 Watts RMS), and a Wet Sounds WS420 (not SQ or BT). The WS420 add lots of "hiss" to all speakers - thinking a newer WS420SQ or BT would fix this? Also, the iPod interface on the CMD5 no longer works, so thinking of replacing head unit (and likely wired remote as all the newer units use the newer MW1 remote). Thoughts? Suggestions? I know the WS420 is what is responsible for the "hiss" - if I wire from the HU to the amps directly, the hiss is gone. The hiss is also present on all the speakers (except subs) even when volume is at zero. Help/advice is truly appreciated!