Mixing subs watts/brands/ not ohms

[deglo]

well i have a 2 channel 300w bridgable amp to 600w
a 900w 12" @4ohms
two 12" crunch older model [not sure wattage] @ 4ohms

the box i have is made for two 12's. but ive only got one sub that i realy want to use and the other two are just laying around.
i want to wire up the 900w visonik and also one crunch sub.
im pretty sure the crunch is around 400w or something i dont know though.
is there any harm in mix-matching subs of much diferent quality and wattage?
this box would be tons more loud with two 12" running.
any advice would be awsome as to wirring or just reasons why not

thanks -matt

[lastdecibel]

***bump***

[quicksilver5157]

well reguardless ur underpowered on ur visonik so it would really be pointless to hook another sub up to the amp.
look up the specs on ur sub and see if it can handle 2 ohms, if u can bridge the amp and run it on 2 ohms... u should be able to push more power.