Amazon had some Klipsch Synergy Sub 12" 300/650 watt BASH amp that is a down firing ported sub for $249.00 shiped Black Friday. 5 years ago I purchased my first pair for my home HT 5.2 system in my small den. They were about $599.00 retail back in 2005, then I found two on Ebay used (1 year old) for the price of one retail. I have had Zero issues with them and when I saw the Amazon add on Black Friday in November for a new one for $249.00 shipped I purchased a 3rd one for my Klipsch Heresy II speakers in the bedroom. These are great entry level subs that have the old BASH amp that has not failed me in the last 5 years. Klipsch has stopped making them a few months ago. They came out in 2005 and I still see them on Ebay in a new sealed box. If you have a small den like me 12X14 they work Great for movies. Years ago when I owned a larger home I had Sunfire Subs (much more expensive and bigger amps) and smoked the amps every few years. A smaller room saved me big $$ on subs...

Good luck with what ever brand you purchase.
EDIT I just noticed you purchased a M8...... hope you get over being sick. We had the stomach Flu for about a week just after Christmas
had to get a IV .... could not eat or drink and ran a fever for a week. Just now feeling normal.