good job keeping the xfl's, the opti subs are horrible for low bass, they have a freq responce of 40hz on the 15", and 50hz on the 12". If you are looking for woofers to do a good job for all around music you definatly didn,t want an opti 1533/1233, If you are looking for a good spl woofer the opti would do well, but I won't say it will be any better than an xfl considering the fact I've seen those xfl's take some serious power, so in an spl application, you're going to do well. I have owned both subwoofers. I've been doing car audio for over 12 years, but just started competeing 2 years ago, and my very first competeing system was with 2 1533D's, and on my American Bass VFL400.1 I bursted 143.5, in a box tuned to specs, by the way those opti's do best in small applications, and for the 1533D they ask for a tuning of 35hz. I went to a competition with no intentions of competeing just to spectate because all I had in my trunk at the time was 2 10" XFL's on a soundstream tx2600 at 1 ohm, which that amp is .5 ohm stable to draw max power. But being the man I am, I competed anyway, with a clamped wattage of about 1336 I hit 139.7 with my 2 xfl 10". I put my 10" XFL's on my american Bass VFL400.1, and my car was way louder than those 2 15" opti's could dream of ever being, I use to have to open my trunk to prove to people I had 2 10", they hit way lower than the opti's to. The motor on those opti's is for impulse buying, the soft parts ****, the thinnest coils you'll ever see, probably have stronger coils on a kicker comp, and a single spider to, if you ran a true 3000 watts to an opti it might last 5 minutes. I see in the pic you have the last year model xfl's, you should see the new ones, well I guess you can say the next years model, and you have the previous models, the new ones have the same basket as the new HD's and the VFL's, all of which I have, they're sweet. Sorry for the long post, just wanted to give you some advise on the woofers from personal exper., and to insure you, you made the right decision, goog luck with your system