running active and passive together

Wow running those two different amps like that might not be the best idea. The McCormack is a lot better sounding amp than the Acurus, you might achieve better results running just the McCormack, but if you want to try bi-amping use the McCormack on top with the passive output for the mid/highs its better suited for the passive side of the MLD. The reason I suggest this is I'm not sure the Passive side of the MLD will drive the Acurus. A few things you need to know when connecting an amp to a passive preamp is the input impedance of the Acurus? What the capacitance of the cables that you are connecting your sources and amps are? And what the output voltage from your sources are? Even if you decide to use the McCormack to drive the mid/highs its still a good idea to know these values to achieve the best results because "A pure passive output is sensitive to cable capacitance, with low capacitance values being preferred". The DNA-1 was originally designed to work well with passive preamps. "For McCormack passive preamps, its suggested that you use cables that do not exceed a total of 1000pF per channel (less is better)". This come from Steve McCormack who designed the MLD and the DNA, you can read more about his passive preamps at SMc Audio on the Q&A section. I hope this helps. Also search here in Agon under Stevemcx read through his answers he makes a suggestion on how to set up the MLD for this type of configuration. Lots of good info in there to.

P.S. Also make sure the PSB Gold i can be bi-amped. Just because theres two pair of speaker connections they may be connected together in the speaker at the crossover.

I am not clear on your question exactly but if you are asking whether both sets of preamp outs can be used simultaneously then I would venure 'yes' as I did exactly that with my McCormack TLC 1 when I biamped with a 4 channel power amp. I'd not even considered it except the manual for the pre indicated it was doable. Check your manual. I used the passive outs to feed the uppers and the actives for the bass channels. Worked fine. You may have gain inequities in your power amps that cause other mismatches but I don't think the preamp will pose a problem.