With the same power going to both...... what will be the advantages/disadvantages of both...... im not sure what iw anna go with....... the RLPs i mean. If Same power is going to both. Which will be louder/sound better...... i i was thinking ported to like 32 hz

The 15's will of course have the potential to give you more output, due to the increased potential displacement. Both the 15's and 12's will sound equally good in my opinion - though of course the 15's may be more impressive due to the increased output as well as the gargantuan look of the things . Disadvantages of the 15's would be the increased cost and space required to run them. It's really up to how crazy you want to get with your project! B)

what mike said..of course the 12's ported will tend to equal out the displacement advantage of 15's sealed.

but i'd recommend a 34hz tuning...offers a tad more output, without sacrificing sq, IMO. mt rl-p 12 sounded awesome in 2ft^3net tuned to 34hz...got silly loud too.

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

Ok thanks for the help....... will a viper 1200 be enough to power 2 12/15's or should i get a bigger amp???

That would be more than enough, Mine is seeing ~500 watts and its plenty to get the driver moving