Hahaha, it's fine.
I got a prefab for my type-x's, it was exactly what everyone one the boards said works best for the x's, 2.0cf @30hz, exactly what i wanted. It even had an awesome inlaid face, so the subs were actually flush with the face of the box.
The boxes for 12" L7's on
ebay look fine, it's the fact that they use the exact same box for 12's and 15's that suspect, the just cut a bigger hole, and then box box ends up being tuned waaay high after you factor in the bigger speaker displacement. I'd say get it if that's what you wanted to begin with.
And honestly, don't worry about everyone telling you to tune low, i went from my 12" type x's tuned to 30hz to my dual 15" L7's tuned at 42hz, and you gotta keep in mind, 42hz is still **** low, i haven't found more than a few songs that really sound much different on the two boxes, other than the fact that the 42hz box sound a lot better for rock music, since the higher tuning accentuates the frequencies of the beat, rather than crazy low synthetic bass.
And i honest to god haven't had too much trouble with regards to transient response, either. My 15's, even when tuned high as hell, by sq-nut standards, keeps perfect time alignment with even quick bass changes in songs like 'what you know' by T.I. and the crazy drum line in 'aenema' by tool.
My roomate has an older 12" L5 tuned @ 38hz, and my 15's tuned @ 42hz have way better transient response and time alignment than his speakers, the 2006 model kickers really have made progress as far as sound quality, but they need a bit more power to get loud than the old models did, on the same coin. I think it also has to do with the fact that my roomate has no idea what a subsonic filter is or what it's for, and i'm pretty sure his amp doesn't even have one. But what i'm trying to say, it the speakers sound waaay better than i thought they would, and even what i 'knew' they would, after owning a 2002 model L7 back in the day. I was really pleasantly suprised by the time-alignment and punchiness of the 42hz box, after how much bashing high-tuned boxes get on these boards. I think proper enclosure size, and ssf/gain/crossover settings have more to do with the quality of results.
Just make sure you know how to tune your system correctly, set the proper gains, don't get crazy with the bass boost, especially with the natural exaggeration around 40hz with that box, and set your ssf correctly, and you'll be happy. Also, even though L7's love to try and extend above and beyond the normal high-end frequency barrier of subwoofers, make sure you cut them off at 80hz or lower, and use your midrange speaks to play from there up, upgrade them if you have to. But a lot of times people have trouble with 'sloppy' sounding gear is when they expect their subwoofer to transition from a 120hz bass-guitar line and still play an underlying beat, or play the notes of tom drums, while still wailing a funky 50hz groove. The lower you set your gains, the less layering the speakers will have to deal with, and the cleaner and more accurate they'll be able to play what they're designed to play, SUB bass.
Anyways, long story short, if the box is what you were looking for anyways, and it's absolutely not a comprimise, grab it if it's a deal.