There is a nice Quicksilver listed here for $575,I recommend this since I own one and think it is real nice. As far as output for sub all you have to do on any preamp is to add a y adapter to the outputs.
With Silver monos. Pre was retired with MIT wire by dealer and was more extended on both ends and detailed but still tube sound. I want remote so am selling it off. Audible Illusions are also great for the price. Can never go wrong with AR stuff but I liked my Quickie once it was retired over the AR. Dealer had both lines and owned both for his own systems so I wasn't pushed one way or the other. I used it with krell amp at first and it made the Krell listenable as did the AR lol. Good luck
If you don't need remote control, there are two Primaluna Prologue 3 preamps now for sale on Audiogon. Does not have XLR out but does have dual RCA outputs. I own one and really enjoy it -- brings 3-D staging, warmth, inner detail, and overall sense of "aliveness" to the music. If you do need remote, check out Primaluna's more expensive models. The Primaluna preamps work best with amps with high input impedance, and if Internet info is correct (which reports your S500 with 75K input impedance), then you're in good shape.
This is what I will offer. I have a amp that is comparable to yours. I have purchased a Consonance T1 preamp new for hundreds less than your budget. This pre is point to point wiring, audio grade caps, tube rectified with minimalist design. Available with remote volume only. No phono. Ok now the sound. In stock form good qualities one would expect from a well designed tube pre. To take this to very good I changed the rectifier with a Create audio ( got one for $50 online although they list $100) great rectifier. Also a mix of NOS tubes tesla and seimens now has unbelievable sound quality and clarity, wide open stage with pinpoint imaging, extended dynamics with good speed and solid deep bass. I took this preamp to demo it with the amp that I wanted to make sure of compatibility and synergy. Much to my and everyone in the room including the dealers surprise the T1 out performed the amplifiers matching pre which is very popular well touted and cost over $6000 . I was getting praise for the performance of this little unknown pre. This pre was better in every area than the 6k ss pre. I do not want to name the matching pre so not to ruffle feathers. If you are interested in what I compared against or where to purchase T1 pre email me. Best
Yes remote is the biggest reason I'm changing it all out. Also, I don't want tubes anymore since they are not easy to deal with for me anymore. I have MS and limited mobility so that's why remote is a must and it has to be full service remote. I ended up getting an Ayre 7xe integrated used and will get Vandy Treo's and a DAC with wire from John at Audio Connection. I have a couple of nice local venders, but the more I listened to systems at other places I felt they were much much better than what I was listening to locally. I feel badly as I like the local guys and wanted to give them the business, but in the end, I have to go with what I like the best. John has gone out of his way to set up everything I want to hear and he had no problem moving things around etc... Locally I told them I wanted to have my TV hooked up too and they said I HAD to have HDMI inputs or I'd have synching problems, but after doing more research, I found my TV has a setting for that, plus I have my current integrated hooked up via RCA's and have no lip synch problems so I dont have to buy the NAD amps. I didn't like how they sounded and that's why I kept looking. I hate wasting peoples time and I'm often too nice to want to say no or to tell someone I'm not going to buy from them. John just made me feel very comfortable and I like his product selection. he sells systems and not just separate products and that's what I appreciate as not all Class A products sound good together.