Outboard Dac's...Do they make a big difference?

ABSOLUTELY!!!! Not a big fan of Mac and can promise either of these DACs will improve the resolution, imaging of the player.

I'd say yes, but with reservation. I don't know any of the three DACs mentioned. I've used PS Audio in the past with good results and I've heard Mac digital in other contexts and your description of it tending to smooth and sweet doesn't surprise me.

A good external DAC/clock combination (one box or two) can certainly improve on what you've got, but it depends on what you've got and what you're going to. If at all possible, try the proposed DAC in your system, using the Mac's Digital Out. There are much, much better DACs than the two listed.

Dave

I recently put a Benchmark DAC on my MC205, Love the upgrade

In my experience an outboard dac is one of the highest return upgrade investments you can make.