Good to know that u got a reliable TPMS now,im sure the ones available here wud b chinese , which usually arent made to last for long... can u kindly illustrate how this thing actually works? wat components it has?
as for the tires, it depends on circumstances.if u are back at home just for a few months and wont b driving more then a few thousand kilometers AND if ur car wudnt be driven by anyone when u r gone back to ur duty , then i think u shdunt change the tires now.they do have some life left in them, although they r 4 yrs old. when u return home next time, change them immediately....
i know getting new tires just now wud sound as a better option but i dont think it wud be a good idea to use new tires for just a little time n they let them stand for 3-4 months...
but if ur car is used by ur family when u r at duty, then certainly u shud change them now...
for sound system, i think u shud post a new thread as this thread only gets visited by steermatic fans and owner, i do hope sum of them are sound system experts too...
regards...