Cubase 6.0.2 x64

Hardware Setup:
AN/DI Pro AD-Converter (SPDIF out) -> HDSP (SPDIF in)
HDSP (SPDIF out) -> M-AUDIO SuperDAC (SPDIF in) --> amp/speaker
HDSP (phones) -> Phones

TotalMix:
Main Monitor: SPDIF

Cubase:
Rec Input <- HDSP SPDIF In
Master Out -> HDSP SPDIF Out

ASIO Direct Monitoring activated

I want to record vocals (Mic -> AN/DI Pro -> HDSP SPDIF -> Cubase audio track)

I click monitor on the cubase audio track. Then HDSP SPDIF In is directly routed to HDSP SPDIF out, the Mic signal is directly monitored at the speakers.

The speakers are in the same room as my mic, so I want the mic signal not in the spearkers, but in the HDSP phones! I can't turn off and on the amp everytime I want to record...

I tried setting TotalMix Main Monitor to Phones, Monitor Phones 1 to SPDIF, activated. Then, the ADM mic signal is available at the SPDIF out AND the phones. However, lowering the SPDIF level lowers the phones level, too. So that doesn't work.

Using HDSP ADAT23/24 out as Cubase Master Out with monitoring the Rec Input will route the ADM signal from SPDIF In directly to HDSP ADAT23/24 out, right?

Setting HDSP ADAT23/24 out into loopback mode will route the signal to ADAT23/24 In. Routing ADAT23/24 In to SPDIF Out AND Phones in TotalMix, with Main Monitor SPDIF and DIM level -inf let me switch the speakers off with the DIM button.

Problem is, with loopback, the ADAT23/24 Out is routed to the ADAT23/24 In IN CUBASE, but not in Hardware/TotalMix, so I can't route the ADAT23/24 Out to SPDIF out and Phones with internal loopback is this right?  (external Loopback cables aren't possible, as the HDSP ADATs are already connected to another HDSP)

How can I playback Cubases Master through Phones, with ASIO Direct Monitoring the SPDIF In (Mic) through phones only, while Cubases Master is set to SPDIF out?