Can a great system make a mediocre recording sound good?

I spend a lot of time searching for well produced recordings as they (of course) sound so good on my system (Hegel 160 + Linn Majik 140 speakers).  I can't tolerate poor sounding recordings - regardless of the quality of the performance itself.   I was at a high end audio store yesterday and the sales person took the position that a really high-end system can make even mediocre recordings sound good.  Agree?