I'm running a V200 on my HD800's and it is a very nice combination.
I also own a tube amp, the Sound Quest SQ84 V2. I haven't done any direct compares, but I suspect the Sound Quest is better. Reason I haven't bothered to compare directly yet is the V200 sounds so darn good on the HD800's. I'm just enjoying it.
So, would the HD800 be a good combo with my V200 and Rega DAC? My LCD-2 is amazing with them.