I would go with option 2 because that's just to much to spend on a sub. I swear by the HGS/DD Velo subs, - have a HGS-18. But, I am not willing to pay that amount of money for it and the amplification and sub upgrade you are looking at gives you a huge overall upgrade.
Heck, then I would take both subs, sell them online, and buy a DD-18 for the money I made off that.
I'm cheap, but my tastes aren't. So, I have to work around both.