You say that this is a mid top box. Any ideas on what frequency you want to crossover to your subs?
Typically a simple mid top box would be a sealed enclosure.
I am a bit concerned about the choice of 2 x 12". The Fane specs for this driver suggest that it is OK up to 5KHz but it is likely to sound rough at a lot lower frequency than this. I have not tried one myself but I would be wary about crossing over at anything above 2 / 2.5KHz with a 12"
Crossing over at this sort of frequency, you are then looking at an expensive compression driver & horn to keep up with your 1KW of mids!
Have you concidered using 10" drivers that will have a higher crossover frequency? An efficient + 108db/W 1" compression driver can keep up with a pair of 10" mids.
Unless you want a lot of trouble and a poor performance you should also concider using a active crossover and bi-amping the cabinet.