Best interconnects used for around $500 +?

If you are on a budget and know how to use a soldering iron then DIY is the way to go. Use AWG 16 gauge fine silver wire dead soft (Riogrande) and untreated cotton sleeve as dielectric. Go for best termination plugs pure silver (WBT or KLE). Kimber's top of the line Select interconnects don't even come close! 

Purist most musical.

Several Years ago when I had a CJ CV12 preamp I used MAC silver cables with good results. Currently I too use Clear Day ICs with my Odyssey system including a tubed preamp. Very nice combo. But I did test drive the Ohno and Purist Vestas. WhileI thought the Ohnos were thin sounding the Vestas were beautiful, musical. They run around $300. I had two sets testing between dac-pre and Pre-amp. Ultimately I went with the Clear Day for additional detail but if you are looking at musicality vs detail with less musicality the Purist were really something. I can only imagine as you go up the line. I tested both through the cable company. May went to test two pair of each to put get the full picture. Regards.

As someone who goes into almost every cable A/B test skeptical that I will hear any differences, I usually end up convinced that I hear some differences only to be left wondering if it matters. Recently I borrowed the Audience  au24se XLRs and couldn't believe how veiled my system became. I looked at the terminals and the connections just to be sure there were no issues there and all seemed well. Left-Right was identical. Extremely disappointing compared to my Audioquest Columbia 2m balanced ICs.

I know you're asking about SEs and not XLRs, but I still believe this is a worthwhile data point whether it be related to build quality, design philosophy, etc. Disappointing is disappointing. When I compare expensive ICs I don't expect to hear that.