Phono Input on A300 overload?

Okay - I've got a new problem in my quest to get my system finished! I'm wondering if the Rega Exact is overloading the phono stage in my Musical Fidelity A300. The Exact puts out 6.4 - 7.2mv which is insanely high and the phono stage is rated at 3.5mv although they don't state the overload point.

I'm fairly certain that the phono stage in this amp is the same as the old MF XLP. There are no ratings for the A300 phono stage other than to say that the recommended input is 3.5mv for MM and .35mv for MC. The XLP, however, states an overload headroom of 28db - real helpful since I have no idea how that translates into mv's! Most phono amps will tell you the overload point in mv's.

Anyhow, on some really dynamic passages on a a FEW recordings I'm getting some audible distortion that I can only presume would be the phono stage being overloaded. These are older recordings from the 70's and it's possible that it's just in the pressing. It's not the amp clipping - I'm not at high volumes and there's no way the MF A300 is running out of juice.

Would a good way to test if it's just in the recording or pressing be to hook the TT up to one of the line level inputs? Those are rated for 300mv so I know I wouldn't be overloading them - I'd have to turn it up to hear, but at least I'd be able to determine if it's in the recording or if it's an overload clip - right?