Not sure all this talk about Home Cinema subs when the OP said "I want a sub to go with them for a mediumish room, just gaming and blasting my music" is good advice from my experience.
I've got a modest Home Cinema setup but have got 2 x Monoprice 12in THX Select subs in a 3.4 x 4.2M room..
For my Study (2.8m x 2.8m) I have a Gemini II in the corner, it's also overkill..
IMO it's about balance, the study setup is great, the bass is amazing for the diminuative size, especially for music/gaming, I'm rocking away now and the nice/taught bass that doesn't generate too much at 10-20hz is perfect for it's intended use, plenty of slam and a good feeling of ~35hz bass which is quite impactful. Casual friends who think their Sonos speaker has great bass think the Gemini II is ridiculously OTT.. I then demo the Home Cinema and think I'm mental.