You want me to make you a bass tube? I'm itching for a new build pretty soon.
Oh anyway, JBL and Infinity share some tech, no doubt. I wouldn't call one higher or lower-end, necessarily, but they both share market pretty fairly. I have a lot of JBL gear in my car now, but that's going away (except the JBL MS8 processor) real soon for better gear in the DIY market.
I can make a shoebox sub all the way to monstrous trunk-killers. It all depends on your design goals and needs. The Infinity unit is "the easy way" out but there's lots of compromises. It has been out for AGES, a very old product.