Single Fi Q18 ported or Two Fi IB315's in IB for ~1600CF (215SF) Dedicated HT?

IT'S A 215 SF Dedicated HT! NOT 1600! It's 1600 CUBIC foot room!!! LOL I've edited the title but it may not update...

I'm in the design phase of my dedicated basement HT found here: http://www.avsforum.com/t/1437601/im-baaack-this-time-with-a-new-project

The room to be built will be 12.5' wide, 17' long and the ceiling is at 7.5' above the floor. I plan on only a single large reclining couch and bean bags for when kids come over. I may try to squeeze in a second row but that's not in the design at this point. I have the space to do an IB but since it's more expensive, would it be worth it?

I've been researching and am intrigued by what I've found on the impact an IB configuration has on the sub-stage. At the same time, it's limitations are in placement options and that it will cost a bit more. For arguments sake and for how the HT will be financed, let's just say the Q18's enclosure and the construction of the IB Manifold/wall reinforcement will cost me the same amount of $. Let's also assume that both designs can be powered by an EP2000 amp and the same EQ device (not decided on yet). So it basically comes down to driver cost and the pros/cons of each alignment...

Here's a breakdown of what I'm thinking:

Single Fi Q18 in a slot ported enclosure to specs - $334

Pair of Fi IB315's in a manifold and reinforced wall - $448

Difference (assuming amp/EQ and enclosure costs remain the same in either option) = $114

Would the pair of 15's in an IB produce $114 worth of cleaner, lower effortless bass?

Also of note is that my receiver (currently) is a Yamaha HTR-6130 but will most likely be replaced with a 7.1 unit with HDMI 1.4 and Audyssey features. My center speaker is a Pioneer Elite S-IW571L and my mains and surrounds are Pioneer Elite S-IW671-LR's. My mains will most likely be upgraded eventually but for now that's what I've got to work with.
Edited by acex008 - 11/6/12 at 7:58am

Or I'm open to other driver/enclosure suggestions to meet my budget and work well in my room with the speakers I have... What about getting the Behringer B1800D-PRO and be done with it?

I am leaning towards the single Q18 as it will provide me with more room layout and location flexibility and the option to easily build another later on. With that said, would the Behringer iNuke NU1000DSP be enough power for one Q18 and provide the needed adjustments without needing to get a separate EQ?

I had emailed Fi about something's and mentioned my HT. the reply email I got mentioned a customer from Florida going with 4 Q18's and a knock-off Behringer amp but he couldn't remember what the brand name was... Is that you?

I'm waiting on some financial stuff to free up before I order my Q18. I'm really hoping I can place the order next week...

I am however a bit concerned with some AVS and HT-Shack member's experience's with this sub. I know to take some of their stories with a grain of salt but it still has me nervous spending over $300 on a subwoofer if it's going to give me the results their experiencing.

I tried finding the thread with the guy that built a single ported one but I can't seem to locate it. I was on my iPhone about to fall asleep when I was reading it and I'm on my PC now but can't track it down. He was experiencing extremely underwhelming output and it may have been due to his equipment but the thread ended. I want to say it was on the HT-Shack forum and from a while ago. I've also seen a few posts here on AVS about people mentioning better drivers since Fi is truly a Car Audio driven (pun intended) company and therefore better drivers can be found for HT use. I'm intrigued though by read the "$700 Playhouse Sub" thread which was my main start at looking into the Q-series ported.

Ricci, I'm interested but don't I want LOW Qts for HT use ported?

So the one you have that your testing would work wonders in a large ported enclosure with 500W going to each VC? PM me your price on it. I usually don't buy used driver's either and am curious how extensive and therefore how potentially "brutal" your testing would be to have me concerned about using it... If your price is reasonable based upon us both not liking to buy used drivers, we may have a deal. I'd ask to receive the testing results tho!

Where should I begin to start modeling a large enclosure for a single Q18? And at what tuning frequency should I go for? My mains go well below 80Hz but I'd like to keep them above 63Hz if I can so they don't break up at 85-90dB's (which is my preferred listening level with 105dB peaks). Also, my listening position from the middle of the port of the sub enclosure will be about 10 feet to 12 feet away which leaves wiggle room for placement.