You can get an old Marantz receiver from 1970's for less, and have a better sound than NAD - check out the link on the bottom.
I like their warm sound. They got great reviews at audioreview.com This a place you can go for audio gear reviews - by the users, and not by the pros ( who are sometimes payed to give good reviews - as you must know ).
You got to be careful when buying from ebay, an old unit like this - many will not work properly - but this one seems like it has been gone through, and fixed up by a shop.
I am listening to one these days, and I like it better than many of the modern offerings that costs several times the price you can get this one for. You should be able to get this for less than $300.
With the sony CD player modified, and a Marantz receiver, and your paradigm speakers, and signal cables, you are in for a treat!
Placement of your speakers are important too - they sound better on a stand. You might want to get them, since they don't cost a lot.
Also, do near-field listening - listening at a very close range, and you will be in heaven, and your wife won't complain, since you can listen at a lower volume.
By the way, wife factor is one that most audiophiles have to deal with - you are not alone.
You might also want to learn about tweaks - they are what you can do to make your system sound even better.
Like pro-gold treatment on all of your connectors - you can buy it for less than $20 - they do make a difference. Google search for them.
Also, optrix CD treament for less than $20 also helps.
The tweak that makes the most difference is burning your own CDR - you can read all about it here :
http://forum.audiogon.com/cgi-bin/fr.pl?ddgtl&1171710271&openflup&3&4#3
This tweak is a must, if you want to tame digital source - like a CD player. Many audiophiles still prefer LP records to digital.
If you do go analogue, and get a turn table later, your Marantz is compatible with it - has a phono stage built in - unlike many of today's units.
Have fun in this hobby - although all the info can be over-whelming, go slow and have fun - in the end it will reward - your ears and heart will thank you.
You are doing the right thing by not spending mega bucks at the beganing of this hobby - many have spent way too much without doing the research, and slowely gaining experience - including my-self. Only then, one is properly ready to a lot on hifi.
There is no limit - one can spend as much as a car or a condo even - chasing this dream. Please go slow and don't make the same mistake many of us audio lovers have.
There is much enjoyment to be had, without spending a lot - if you do research.
Another suggestion is to get headphones - sennheiser px-100, or Koss sportapro for less than $40. Your room acoustic will not come into play, and ruin the sound. Also, you can listen deep into the night with them.
Headphones through the Marantz receiver sounds good !
Also has a really good receiver section, if you do listen to radio.
p://www.audioreview.com/cat/amplification/receivers/marantz/PRD_118646_1593crx.aspx
http://cgi.ebay.com/MARANTZ-2270-COMPLETELY-SERVICED-NICE_W0QQitemZ260172626412QQihZ016QQcategoryZ3279QQssPageNameZWDVWQQrdZ1QQcmdZViewItem