can def vouch for dalco's service, had my CTR done this weekend and its Superb! it was worth the 260 miles round trip!
the amp you have wouldnt be powerful enough for your sub (though it will work just not as good as you would think), since its 10" it'll require less than a 12", best to go for a mono amp as dalco said. Do you have rear speakers? Try and match the amp RMS output to your speaker/sub RMS levels.
you could use your existing 4 channel amp to power your front and rear speakers, get a monoamp and power your sub, would sound ace after that! dont forget sound deadening too as it does make a difference!
my door has a nice 'thud' sound when closing them