[Tunecrew]

This is what I did when upgrading last year - bought a used one on eBay (which is a first for me - normally buy them new) - 2015 15" fully maxed out (fastest i7, 16GB, 1TB) and including the GPU, so it basically benchmarks only slightly slower than the top of the line current model.

I already had a TB2 hub and other TB2 peripherals and extra MagSafe 2 power supplies, so no additional investment in adapters, etc.

The kicker was the unit I bought has been purchased less than a year before I got it, so it was still eligible for AppleCare (you can check this w/ the serial number that most reputable eBay vendors provide). The time has probably passed for this, although you could still get a unit where someone else has already gotten it.

All in was US$ 2,050 including AppleCare