I've recently been putting together a HT system and my next step is a sub.
So far I have a Yamaha RX-V473, Klipsch RF 52 II towers, RC 52 II center, and some cheap surrounds and sub from an early 2000s Sony HTIB. The room is 1000ft^3 and is a bedroom where it will be used for 50% HT, 25% music, and 25% video games. I am most concerned about HT performance.
I'm familiar with DIY sub boxes. I've done some for car audio, and have no issues building a ported box or doing the math to design them. I have access to the tools, and "1.8 ft^3 @18Hz with 15in^2 of port area" is enough information for me to design the box myself and get it built. I don't need blue prints, just some help on driver and box choice. I have a couple year of car audio experience, but not much HT experience.
I've been looking at purchasing the Klipsch RF12D for $300, but think for $300 I should be able to build something better. My biggest concern about the Klipsch is that people say it can be boomy, and doesn't have the extension below about 30Hz. My goal is to match the output, while digging deeper, and sounding cleaner. If I can't do that for $300 (flexible budget), then I'll go with the Klipsch.
I have about 18"x18"x18" available, but can always go taller if need be to get some more air space.
$300 budget including driver, amp, and materials. Looking for low extension and tight response in a 1000ft^3 room for mostly HT use.