nub >>> pre-amp u mean?

RM200 for 2 x 10" woofers?
depends on the quality lo

from my opinion
unless the 4ch is very high power output
else yr woofers don work well
if only yr 4ch all power in on the woofers only

for woofers, it'll b the best if u using monoblock juz to hit the woofer
the less channels, the less percentage it wont goes overheat
maybe u can think of 2ch amp

basically
to me u juz need add some bass for yr audio system
so add on woofers would do the job

this is what i know
maybe some other pro can help to hav better n reliable answers

oh~ that nub control unit ka
some good amps only come wif that stuff

if u wanna b good u hav to do sound proof as well lo

monoblock is for woofer la for better performance
it can connect 2 woofers the same time if handling power enuf


if wan things to b perfect then hav to b match