The Rotel has gone - was it you?
Still reckon you'd be better going passive - and not from the headphone output on a CD player as it's usually a manky little general purpose op amp output - especially since you've spent a lot of money on (literally) transparent power amps.
Trust me, you just need a volume potentiometer in a box. ANYONE could make one for less than a tenner, yet 'audiophile' passive pre-amps sell for silly money to gullible fools.
<note to self - simple money making opportunity>
If you really want a pre-amp, those fromage pointed out will fit the bill, but why introduce more circuitry when you don't need to? It can only degrade your sound quality, but by how much depends on what you choose.
Have a read here. The circuit at the top is all you need for line level sources. http://sound.westhost.com/project01.htm
"Two very small men cutting steps in the roof of the world"