I've been considering getting one of these subs but I am curious, I'm hoping that they are under rated a bit. And i know it is generally a good idea to over power the subs rather than chance clipping the amp, and I know how quality they are so I must ask will I be safe running one DCON on an Alpine MRP-M650 at 600w? I know that I can always gain down the amp but does anyone think they'd be alright at nearly full power?

My other consideration is the 'moderately rated' Skar IVX 15

I would highly suggest looking elsewhere before considering SKAR.  

 

As for the DCON, you're going to be hard pressed to find another sub that performs as well for the money.  While it's okay to run a little extra power in most cases I don't think double the RMS is recommendable.  The amp is rated at 400wrms @ 4 ohms.  Why not order a 4 ohm SVC DCON and then in the future if you decide to go with two you'll still have that capability.  You don't need to throw full RMS or more at one in order to get everything it can offer and that goes for any sub.  The most important thing to consider and spend your time, effort and money on is making certain the enclosure is as close to perfect as possible.

I agree 100%

I would move up to a gcon if you want to run watts 600rms.

I would highly suggest looking elsewhere before considering SKAR.  

 

As for the DCON, you're going to be hard pressed to find another sub that performs as well for the money.  While it's okay to run a little extra power in most cases I don't think double the RMS is recommendable.  The amp is rated at 400wrms @ 4 ohms.  Why not order a 4 ohm SVC DCON and then in the future if you decide to go with two you'll still have that capability.  You don't need to throw full RMS or more at one in order to get everything it can offer and that goes for any sub.  The most important thing to consider and spend your time, effort and money on is making certain the enclosure is as close to perfect as possible.

Listen to this man, it's as if I wrote that post.