Audio Set-up question

[jbarnesiii88]

I am new to car system audio. I am not new to wiring.
I have HU is 50Wx4 with 4 small speakers that can handle up to 300w.
I also have one 12 inch sub that has 175W RMS, max 500W.
I am debating on purchasing an amplifier that is a 400W 2 channel amp.

I have my speakers wired directly to my head unit. If I connect my amp and my 12inch sub to my HU, will I ruin my smaller speakers? Or, since the speakers are wired directly to my HU, will they not be affected by the amp? I do not want to blow my small speakers!!

[Kevinl]

wont be affected as long as it is wired correctly

[jbarnesiii88]

OK, next question...
I acquired an 8 inch sub as well, but it is 8omh.
I want to hook my 12 inch sub and my 8 inch sub to my amp.

Amp specs: 400w, RMS rating: 4ohm; 50w x 2 chan;-- 2 ohm: 75w x 2 chan;-- Bridged, 4 ohm: 150w x 1 chan
Sub specs: 12 inch: 175 RMS at 4 ohm
8 inch: 120 RMS at 8 ohm

Am i able to hook these 2 subs up to the amp without frying it? And what sequence would I have to wire the subs if I can?

[mylows10]

dont use both subs ,they'll cancel each other out and wont sound very good.use one or the other ,or get 2 matching subs