How much difference in sound?

I would keep the amps, even after you upgrade to something better. There is quite a bit of enjoyment to be had from those amps... perhaps for a second system.

I like your speakers too... Your present setup should be pretty good as they are... Good mid-fi system.

Seems like you caught the upgrade bug - please don't go ever upgrading like some audiophiles, and dig deep into your bank account.

See if you can live with the present system, before upgrading - should be enjoyable system - what CD player are you using at the moment ?

If you upgrade the CD player, and cables ( unless you already have good ones ), you might not need to upgrade other parts of the chain.

I like the NAD/PSB combo.

I would try this before the amp.

I respectfully disagree - at least in my listening experience, I found the source to be quite important part of the chain !

The onkyo CDP is holding you back - while the rest of the system is good mid-fi.

If you get something like this, you will definitely hear a difference - hopefully satisfied enough not to upgrade, at least for a some time.

http://www.audiogon.com/cgi-bin/cls.pl?dgtlplay&1240452353&/McIntosh-MCD-7008-CD-Changer

http://www.audiogon.com/cgi-bin/cls.pl?dgtlplay&1239488831&/McIntosh-MVP831-original-packi

I don't know which one is better - you might want to read reviews on them - but I have 7000 series, and I simply adore it!

Hope this helps...