Hi msm_1,
I use balanced splitter cobbled up using Gotham interconnects. I don't feel that there is any degradation as it is just a short run of less than 6 inches.
When I used the Y splitter before, I also did not feel any degradation. I look at the Y splitter as just an extended part of the RCA jack.
I have done this using different MIT interconnects such as 330E, shotgun, CVT, Oracles and it worked fine in every case. I suppose going through the Spectral RCA jacks and through splitters do not make much of a difference as Spectral's internal wiring and jacks are pretty standard.
If you wish to really experiment, you can bypass the SDR's RCA jacks and solder your interconnects directly to the SDR's board.
I have changed the internal wiring of one of my Spectral DMC 20 preamps from the input RCA jacks into the board and from the board to the output RCA jacks; at the same time, I changed the RCA jacks to Cardas brands and there was real improvement with these tweaks. Be warned though that this voids the warranty.
Sam