Now it's subs

I've lived in disdain of subwoofers for years.  The poor integration and indiscriminate screwing up of the voicing of the delivery.  Today I was just testing a recovered old active Gallo sub and it made some just okay speakers sing.  What ?!?!?  Arrrggghhh!!!

Now the contemplation of a very decent sub to pair with my Merlin Black Magic monitors.  System as follows:

Naim UnitiServe server with Pardo power supply, Naim DAC, Manley Jumbo Shrimp pre, Manley Mahi Mahi monos, all Decware cabling.  Thanks for any input regarding fast subs that improve all aspects of imaging, attack, voicing and impact.  Musical tastes mostly jazz, blues, Celtic.  

Thanks so so much in advance.
                                                        Doug