I have always used the built-in phono stage of my amp(s) to hook up my turntable - and I've always wondered if adding an external stage could increase the quality. But I have no idea how the quality of different phono stages could be judged and compared... is anyone qualified to comment on this or has first-hand experience? I think my Denon PMA 1600 has a decent enough phono stage - but would a mid-priced external device (such as a Cambridge or a Rega product for £200-300) be an improvement already, or would it have to be a significantly more high-end one?