CustoMac Budget ATX build, can you update parts easily later?

I'm going for a CustoMac build. I was trying to put together an i7 6700 build but budgeting not alloying right now. So Im going for the following:

Intel Core i5-6400 2.7Ghz
Crucial Budget 32GB RAM
Gigabyte Z170-HD3 Motherboard
Gigabyte Nvidia GTX 750Ti Graphics Card
Corsair 300R Tower Case
Corsair CXM500 PSU
TP-Link WN851ND Wireless PCI Card

I was wondering how easy is it to replace parts later if they are on the CustoMac recommended parts? For example, if I want to replace the CPU for an...

CustoMac Budget ATX build, can you update parts easily later?