Im not sure if Im in the right section but here goes, have recently installed a pioneer GM-6400F 4 channel amp, TS-d1602R 6.5 front speakers, TS-D6902R 6x9 rear speakers & 2x convertors to use the existing headeck. Anyhow the problem Im getting is low frequency noise coming from my headeck especially in low volume, its like when Im accelerating I hear it going with the acceleration & also when listening between tracks I hear it & its annoying. I have been advised to replace the headeck & this will fix the problem, anymore advice on this will be appreciated. BTW when cranked up a bit the speakers nearly replace in having a subby installed (well nearly).

Possibly sounds like a shielding issue to me.
1. You said you get the noise in between CD tracks. Crank the volume and pause a CD - is the noise still there? If it is gone completely, it's a head unit issue. If it is still there, it's a shielding issue.
2. Try unplugging and turning off everything electrical in your car and see if it is worse/better (for example, accessories into the cigarette lighter, interior & exterior lights, etc) and see if it makes any difference. Turn them on individually one at a time with the volume cranked and see which is the cause.
3. Is it coming out all speakers or just 1/2?
4. Try relocating harnesses to slightly different locations behind the head unit, or have harnesses crossing each other at 90 degrees (don't run them parallel). Try wrapping wiring with kitchen alfoil bit by bit until you can isolate the one/ones causing the noise, then shield them properly or replace them with shielded wire.

Thanks for your advice flyboy. Have tried the cd test but I havent got a pause button in my stock headeck, had to rely on the pauses between tracks however there was only a slight noise, this could be due to the quality of the cd copy perhaps. My hi/lo converters are located behind the back seat for the rear speakers & the front is located behind the glove box. Ive also tried regrounding the earth wire from the amp & only helped slightly. yes the sound is coming from both speakers. I havent tried your advice on No.2 yet. If its any help the noise is more apparent when the radio is on especially when accelerating @ lower to mid range levels. Btw my car is 2007 vrx 380 series 3 model.
Thanks again for your help

Okay, so I think the next step is to reground everything - your headunits and amps - each one to at least two different points, with good quality shielded wire. Sounds like your grounds might be giving some of the trouble.