I once owned a C-38 Pre-Amp, and the Phono Stage was decent for a good MM Cartridge.
Being candid about what they throw in, McIntosh won't ever throw in garbage. But in truth, how much money you figure they invested in parts into a Phono Stage? Maybe $25 in parts? Probably a $300-$400 decent modern Phono Stage will best what's included in the Mac.
Don't ever be reluctant to use an external Stage. McIntosh thankfully incprporates mucho inputs, so you can hook up virtually any gear to your hearts delight! This is what I do! My Main Amp is McIntosh, Phono Stage is the Battery Powered Sutherland PhD. Mark