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.)
I used to have a Parasound 1200 amp and used their 1100 preamp (I think that was the model) The combination worked very well. Also, Bryston's BP25 is a great pre for the bux. You will enjoy much better sound with either of these that I'm sure you can find used than with the Onkyo. Let us know what you decide on.
Upgrading the Onkyo will make a bid difference. Try to find a McIntosh C712. It has a processor loop and beat many other preamps (in my system) with its beautiful sound quality. Great preamp for the money. Arthur
I love my little Parasound hp850 preamp. It matches well with the hca 1000 thx amp. Linn LP12 > Parasound > Tannoy Revolution 3's. That's it.
What do yall think about the aragon 18k as a preamp with this system?