I have figured out the BTU of my house and would like to install a mini split system. I think I need a 6000 BTU unit for each of 6 rooms and I would like to put a 18,000 BTU compressor on each of the sets of 3, but I don't see them marketed in those combinations. My house is about 30,000 BTU total. How do I find out if my plan is appropriate and how do I go about buying 6 6000 BTU ceiling cassettes and 2 18000 BTU compressors? Thank you.