Best Pre-amp for $500??

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

Digital inputs?  as in Optical?  USB?  Coax? So,  you are confirming the questions that you want an on board DAC?  I can understand that.  I would only comment that the quality level of a few of these preamps mentioned are far above anything that you will likely find at their price point with a built in DAC.  I could be wrong.... I can say that I've tried a few under $100 DACs and have been pleasantly surprised.  I'm sure that you could also get recommendations there.... On this tread and the last, Classe CP35 has been mentioned.  I have seen these on Craigslist (might have been a CP30) for as low as $300 and they do go regularly for under $500.  Not as detailed as some of the others, but smooth and musical....
Good luck with your search. 

Just did a quick search on Fleabay looking for a CP35 and came across this... I've owned 2 Yaqin products,  they were both quite good.  This looks to be a steal and later you can roll tubes.... I'll point you to a couple DAC's under $100 if interested. 
I hope this helps,  Tim
http://www.ebay.com/itm/YAQIN-845-12AX7-Class-A-Hi-End-Vacuum-Valve-Tube-Hi-end-Pre-Amplifier-110-24...