Hi Terence and Timbana,
The TAK TA300Bs really are something special (I love them in the LIO DHT PRE, and in the L2 Signature Preamplifier).
Glad you both are also enjoying them.
The SV811-10 has more bass and "thicker" midrange, and more relaxed top end. With certain speakers and headphones, they
have a nice synergy. I can see how they are a good match with the HD800 headphones.
Regarding the ELROG 300B, they are currently with an L2 Preamp that out for review (also has the stock EH300B Gold Grid). From the time I had with them in the L2 and LIO DHT PRE, they seemed to have a sound signature that resembled a mix of the KR PX-4 and SV811-10. Keep in mind that I did not have much more than 25 hours of burn-in on them. So I'll have to wait a bit until I get them back before I spend more time with them, but there were sounding very nice!