Well, let's see if an opinion of <b>the girlfriend</b> matters.
You don't really ever want to mix sub brands <i>OR</i> sub sizes, even if they are the same brand!
Instead of getting the benefits of both like you would hope, instead the exact opposite, you become limited by the weaknesses of each.
For example, you might be thinking of doing this so that you could have all the low extension and 1st octave strength of the 15" sub, while also having all the speed, accuracy, and strong 2nd octave performance of the 10's... I mean, you told me those were your initial intentions.
INSTEAD however, you will end up with the opposite... If the tens bottom out before the 15", you will end up having them bottom out on low loud notes, meaning the 15" won't ever reach it's low end potential, because surely you will turn it down when the 10's bottom out, right? It only makes sense that way.
Likewise, while the 10's are performing crystal-clear in the higher faster kick-drum range, the 15" moves slower, a little muddier, and it will cloud up the sound somewhat, that muddiness will be audible, much in the same way that the 10's bottoming out would be.
Anyways, my point is you simply end up with the compromises and limitations of BOTH speakers, rather than the best of both worlds! And believe me, after investing into that amp for you (plus sound stuff), I don't think I want that, sorry. You might as well, just use whatever you had before.
Only run one, since you have the ten, I <b>definitely</b> would recommend getting the second ten though.
If you had room (and I know you don't) for two tens and a 15" sub, you would have been able to pick up maybe three tens instead of two, and build in even more airspace per sub than your sub is getting now, that should help get not just your total SPL up, but will also extend the low frequency response... It will sound SICK and you will be surprised just how 15"-ish you can get those tens sounding! <img src=/images/forums/snitz/eek.gif width=15 height=15 border=0>
However, I know there isn't enough space to do that... unless I didn't check it properly... I can take a look.
Anyways... this is my advice, honey.
<hr width=60% noshade size=1 align=left><b>Random:</b> <i>Next time...look in the mirror when you say Selfish.</i><img src="http://www.hyundaiperformance.com/images/forums/snitz/thumbup.gif"></img>