OK 1) no caps. 2) what vehicle do you have? 3) those type x subs will handle well over 1kw no problem each 4) why limit yourself to only alpine products? (not that they aren't good just wondering.)
There is a lot more to doing a proper set up than just throwing a bunch of equipment in. For instance, what type of music do you listen to? That will determine what type of box you will most likely want (sealed/ ported/ bandpass/ t-line/ etc.) What are your wood working abilities? Be aware that the specific sub you use will determine the size and tuning (if you go ported) of the box you use. This could be a limiting factor in your decision since the Type X 12 needs somewhere around 1.8 cubic feet of airspace per sub. That's after sub and port displacement. Some other brands you may want to look at for subs are DC Soundlabs, Fi car audio, Digital Designs, RE, RD and there are more depending on what sound your going for.
Now someone said to get the PDX5. Great amp. Unfortunatly it probably won't be enough power for 2 Type X 12's. The sub channel only puts out 300 watts. Not even enough for one of those subs. The nice thing about the PDX amps though is that they are "small" and stackable. A better solution would be something like the PDX4.100 or PDX4.150 for the interior speakers and 2 PDX1.1000's for the subs. That is if you are dead set on those subs. I have a Rockford Fosgate 25 to life Power 1000 that is brand new I'll let go for a grand. Things sexy
But its a 5 channel and does 110x 4 and 995x 1 on the sub channel. And that's one of the highest powered 5 channel amps you'll find. Another option is the Memphis Big Belle.
Anyways, as you can see there is a lot that goes into a proper car audio system. I haven't even gotten into powering the amps, head units, why not to use caps and get a small second (SEALED) batt. instead, wiring a system properly, etc.
Whatever you do, don't let Best Buy do your install. Go to a reputable shop specifically dedicated to car audio. Or better yet, research your ass off and do it yourself. It will be more satisfying.