I need help with selection of a pre-amp

I currently have paradigm reference studio 80's, a parasound hca-3500 amp, and a denon dvd 2900 as my source, and i am using an onkyo reciever as my pre amp. I am looking for recomendations on a pre amp with this combo. I would prefer to buy a used one and am willing to spend up to $500. i would also like a thru put so that i could run my home theater pre amp though it but not required.(just as a side note i also have a parasound hca 2005 and paradigm refrence surrounds and center and i am looking to integrate my 2 channel and 7.1 channel systems.)