Yes - occasionally.

I have a DT50, several Marshall amps and a Spider Valve MkII 212 as well as a MkI 112, so depending on what I'm doing I will take the HD500 with one or the other.  This afternoon I used the HD500 into the FX Return of my Marshall JVM205H 50w head and a Marshall 4x12 loaded with Celestion Vintage 30 speakers.  It sounded great

The HD500 with the Spider Valve is pretty straightforward.

I plug one of the 1/4" outputs on the HD500 directly into the Spider Valve's Power Amp in socket and completely bypass the front end of the SV.  I set the 1/4" output switch to LINE and set the output mode on the HD500 to Combo Pwr Amp

At low volume, I find that using FULL amp models and cab models in the HD500 works well into the SV like this, but when at gig volume levels, the PRE amp models work well in general - and with cab modelling turned off (as the SV's speaker handles that).  The only controls that work on the SV are the Master Volume and Presence when using the Power Amp In socket on the SV

If you have a MkII SV, you can alternatively plug the HD500 into the front guitar input socket and completely disable the DSP section by holding the TAP button down as you power the SV MkII on.  This also works on the Spider IV 75 and greater.  It may work on the SV MkI and Spider III too, but I have not tried this.

My SV 112 MkI has been modified a little in that it has a Strymon SVpre and a Celestion G12K100 speaker fitted, so it will sound a little different to the stock amp - even if I just plug directly in to the power amp, but my SV 212 MkII is completely stock with V30's, so hardly any different to a MkI 112

Whether you find the PRE amp models work best for you with cab modelling off as I do when plugging into the Power Amp In of a Valve Amp at gig levels or whether you find the FULL amp models work better with cab modelling on or off will be a matter of experimentation for you and it's what works best for you at the end of the day.

Plugging into the DT50 with L6 Link is another story as the HD500 and DT50 are designed to work together and the DT50 is controlled by the HD500.

How you connect the HD500 to your amp is of course up to you ultimately, but to start with: for gig/band rehearsal levels try using PRE amp models with speaker modelling off, and; for low volume levels for quieter home practice, you might find the FULL amp models with cab modelling switched on are better.  Ultimately you want to achieve a good sound, and there are a number of ways in which you might do that.  What works for me may not necessarily work for you and vice-versa.

Regards

Nick