As of a few days ago, Marlin supports very large files with using very little RAM.
The data for the sample was always held on disk, but the peak data was always in memory. The peak data has been moved onto disk as well, which means Marlin is able to load large files.
My tests on a 78meg mp3 show that physical RAM marlin needs is about 20 meg, the space on disk needed is about 1500meg though. Dunno how this compares to other programs. All I can test is Sweep which doesn't appear to store anything on disk and so dies while trying to load the sample.