I love my Rg1570z...I am considering switching out the stock pickups though but am always interested in researching other guitars

I was looking at the ESP horizon FR II...the guitar looks amazing. Does anyone have any input on this guitar or other guitars that are comparable (or better) than the Ibanez Rg1570?

I also own a peavey 6505+ head and mesa 2x12 dual rectifier as well as a maxon 808 for overdrive. I love playing metal (all different types of genres) and melodic instrumental pieces

you can't go wrong with an original ESP and horizons are excellent metal guitars...
Meh, my advice, mix it up. Why go for multiple super strats? That's boring, try going for a Les Paul, Explorer, maybe even a Jackson King V or a Kelly (my KV2 was definitely a good choice). Mix things up and find other things that you like. It will probably inspire you to play different things and make guitar a lot more enjoyable.