Welcome to ProCooling!
You must have some money, to be willing to throw it around like that!
Your block selection is good. What you have to keep in mind, is your objective: lower the temps a little.
A simple upgrade to an Eheim 1250 won't do it. Adding any radiator will.
Now I never recomend buying a BIX, any BIX, because anyone can do better with the money, by buying a heatercore. In your case however, you clearly stated that you didn't want to get into case modding, so you really don't have any choices there.
But otherwise, I'd recomend that you sell the pump and BIX, and upgrade to an Iwaki pump, and heatercore. But hey, that's just me.
In your proposed setup, I think that only one microBIX would work just fine. If anything, I'd look at making one loop, and run everything in series, except the rads, and it would benefit from 1/2" tubing, so if you're not there yet, then stick to plan "A".
Good luck.