Best Pre-amp for $500??

Cambridge 851D might be something to look at if you don't spin CDs or have another player you want to keep. I've not heard the 851D, but would think its for the most part an 851C without the transport.

A sunfire amp drives Maggies.  Outboard DAC is dealing with an Apple TV and Mac/iTunes.  Still have a Cal Audio CD player, and sometimes use a Yamaha tuner.

I had a Sonic Frontiers pre-amp but it blew one channel and the remote is busted too.  

Get the aragon 28k preamp if u can find one.
I have owned it for 20yrs.
In those years, it beats all my new purchases to replace it. Musical fidelity ac3r, rogue audio, simaudio 740p.

During my process to upgrade it, i brought it for comparison with accuphase 2410, ayre kx5, ayre k5xemp, jeff rowland capri, mbl preamp, the aragon never paled in comparisonin terms of Clarity, openess and dynamics.

I finally bought the sim 740p based on reviews and without audition.

Sold the 740p after 3months. 

Still stuck with this vintage, its simply irreplaceable.

Oh yes, forgot to mention it also sounded way clearer than the mark levinson 326s

well, I answered your thread for a $400 preamp.... The suggestions here are similar...
When you get to that $700ish price point,  things change....
At that price I would look at an Adcom GFP750 (Only this model in Adcom).... I would look for a Muse Model 3 or Model 3 Signature if possible.  I would look for a Bel Canto Pre 1.   These all sound Great, the are all single ended or balanced,  they all have remotes....
I hope this helps,
Tim