I don't know your CD player Phil, the only contribution I can make is when I added the Musical Fidelity X-DAC3 to a Sony 777ES (CD, SACD) player, and it made a significant improvement - more detail and tighter bass.
The Benchmark has good reviews, here's a link to a recent review:
http://www.stereophile.com/digitalsourcereviews/886/
I would try and get a DAC on demo for a few weeks before investing any $$$$$.