I've narrowed my choice of sub down to a Boston Pro 10" 4ohm or an IDQ 10 v2 2+2ohm.
As I'm yet to have the opportunity to audition either sub I've had to form an opinion based on their reputations.
I intend to run the sub, off a bridged 400WRMS amp, in a sealed box firing forward through the back seat armrest hole.
Can anyone here, preferably someone with experience of both subs, help me to decide which one and/or recommend appropriate box sizes?

I had the exact same setup except with an IDQ12- had the 12 in a 1.1ft3 sealed box with 400rms and had it facing forwards.Very nice indeed... Only thing better was when i added the second sub and more power I personaly would recomend the I
DQ sub

I just bought two Boston pro 10" subs with 600wrms on tap for each and these things go deep (.75 cubuic foot)

Both excellent subs when used properly. You will be very happy with either.
Go on price/looks IMO......

O.K. the pros and cons as I see them: Both subs have excellent S.Q. and work well in a small box,the IDQ may have slightly more output on my amp but the Boston should ultimately handle more power if I upgrade it. The Boston is the looker but costs a bit more and wouldn't even be seen in my install unless I spend more money putting a glass back in the box. The Boston is available now but I'll have to wait a few weeks for the IDQ.
From about ten really good subs, for one reason or another, I have managed to narrowed it down but I'm finding it difficult to separate these two.

as a related issue, boston recommend pretty small enclosure sizes for their subs (1 cube for 12's). my question is, do you HAVE to use such a small enclosure, or is it permissable to use a larger one?

the bostons dont go very loud but their SQ is great

On another thread RetroPimp said his gf has a pro 10" in a 1.8cf box and it sounds great. On the other hand the guys I've talked to that sell Boston seem to recommend .5cf like Boston do. Boston recommend amps from 50-1100WRMS so I think they would be good in a larger box so long as you don't give them too much power. I was thinking .75-1cf for 400-500WRMS but I'm just guessing. What do you think claf? What do you mean they don't go very loud? Compared to what?

You can certainly use larger than recommended enclosures for almost any driver, in a sealed box so long as you don't exceed the Vas spec (bad).

More box basically = more bass low down + bit more efficiency at the expensive of some power handling.

ie more output from larger box requires more excursion so it excursion-limits earlier.
The total bass output is basically the same, but you move the output profile downwards where more excursion is required.
And that's why recommended boxes are smaller.

Hey Critter, how are the P.G. Tis going? Do you think I made a mistake crossing the 10" SVC off my list? Would they go louder than the Bostons,IDQ?

There is a civic that has done 150dB with 2 pro's in a small sealed enclosure... so they CAN go loud...

But I would go the IDQ's because of the price factor...