I have the EP-175 and I've finally had it configured properly. It integrates quite well into my HT system.

The room is about 300 sq. feet and while I certain get bass, it's not earth thumping.

Is it better to get a second sub for the back of the room, or just replace the existing sub with a large one?

go ahead and get a second sub, and make it a large one..!

you could link up another sub, but that room(20x15?), isnt super big. i would think if you just got one good powerful sub, it would get the job done. plus, at that paoint, you could try and sell the EP175 to help with the cost for the new one.

bigjohn

I'd opt for scrapping the small sub and buying a big monster to replace it. My success with 2 unmatched subs was mixed. Maybe 2 EP175s would work well, but you're not going to get the depth of the bigger sub, right?

I have an EP350 in the same room size currently and love the performance. However, it will be soon all moved down to my new HT in the basement. The overall room down there is closer to 900 Sq Ft. Will see how the good ole 350 performs, then may get another 350 or who knows maybe a 500

Sounds like you and Saint could work a deal?