Better invest that money elsewhere. Here's why: Amarra is aimed at studio mastering; playback is only a small part of its functionality.
It takes a lot of computing power and memory to have it running smoothly. Playback gains are audible, but there's more to be gaine if same money would be invested in amps or speakers.
Audio merits of Amarra would be in the 50-80 pound region IMO.
EDIT: other options would be to invest in rega dac. IMO there is more sound per pound gains in speakers, but as you seem already settled on rega speakers and amp, my next choice would be rega dac.