I am in the exact opposite camp as Stehno........Oh well such is life. The pre-amp has always had the biggest impact on my sytems performance, all things being equal, except for perhaps the speakers. However, having said that either component you upgrade (amp, pre-amp) is going to have a pretty significant impact. You mention your dealer does not stock the 140 does he/she stock or have as a demo the 17 and if so will he/she let you bring it home for a demo. No disrespect intended to Stenho we all have different experiences.
Chuck