One more that I would recommend would be a Klyne preamp. I'm sure the Klyne, Threshold, Classe and Forte would all sound better with your Aragon amp than the Parasound or Vincent would.
Of the follow up replies, I would say that Robr45's Quad 99 is the best of the lot. I would avoid the tube preamp reco's, and believe me, I love tubes, owning a tube preamp and amp. However, synergy is very important, and your Aragon has a rather low input impedence of 22Kohms. I know many will speak of a 1:10 preamp:amp input impedence as the minimum, but I would stress that this is the MINIMUM. From my expeiences a 1:50/100 ratio or more is much better, the higher the better. So I would not consider a tube preamp with an output impedence of 1K or more at all.
I also would not consider the Proceed AVP. I have owned many high end Processors back when I was trying to make HT the center of my universe, about 8 years ago or so. I tried many high end models from Proceed, Krell, Classe, etc. While they were great for HT, none could compete sonically on music with a good stereo preamp, like the Classe CP-60, IMHO.
Cheers,
John