MC 402 vs. MC 7300

Depends on the speakers that you are driving. I run a C45 into an MC402 into a pair of B&W 803's without ever approaching the limits of the amp while pushing the speakers about as far as they'll go. Other than available power, the Mcintosh ss amps sound remarkably similar. I doubt that anyone could tell the difference between a 402, 252, pair of 501's, or an integrated unless the current limitations are reached.

When I went from my MC252 to my MC501's I was very surprised at how dramatic the difference was and I normally listen at very low volumes. I immediately heard more accurate bass and much fuller mid range. If you can, listen to the MC501's before you buy the MC 402.

I have a pair of Dali MS5's. Would I be best served by going with the C45 first?

Winger - Upgrade the amp before upgrading the preamp. The amp has a more difficult job to do - driving a difficult load. The signal levels fed to the preamp just aren't that difficult to deal with - particularly if you are feeding a signal from a cdp. In short, getting the amp right is a harder design task when it comes to home audio. There is the school of thought garbage in garbage out - profferred by those who recomend upgrading a preamp first - that approach is inapplicable for this scenario.