The main difference between the SP 1.7 & 2.0 is a new digital chip- analogue pre amp is the same. Refer to Bryston site:
http://www.bryston.ca/BrystonSite05/pdfs/PREAmplifiers/SP1_7toSP2Upgrade.pdf
http://www.bryston.ca/BrystonSite05/pdfs/PREAmplifiers/SP1_7toSP2Upgrade.pdf