The Squeezebox is not a "stellar" 2-channel source.
Are you running it analog or digital into the 3802 ?
Adding an analog pre will not accomplish anything IMO.
What would an analog pre offer over the Squeezebox's own volume control, or the 3802's analog pre?
Using the Squeezebox's digital out into a better DAC would certainly yield sonic improvements.
But then you are still left with the 3802 as your analog pre, which isn't the greatest either.
For an analog pre, the Bel Canto Pre3 is quite good for the money, has HT bypass, looks good.
Use the Pre3 along with something like a Bel Canto DAC2 ( very musical ) and you will have some great sonic improvements.http://www.belcantodesign.com/prod_PRe3.html
You can probably buy both pieces used for $1700 at Audiogon.
Another interesting & affordable piece is a Monarchy M24 2007-Edition -> a tube DAC, solid state DAC, tube pre-amp.http://www.monarchyaudio.com/
BTW, I love my Squeezebox v3 ! ..... and have owned DAC2, Pre3, 3802 in the past.