The Power Bar would be the best choice to drop the noise floor on the whole system.
The power supply for the DI/O, it is NOT a wall wart

, is quite a bit better than the Stancor. It will reduce noise and give the DI/O more dynamics and a tighter bass.
I would suggest you replace the Type 2 interconnects with either the M-80 or NITRO. The older design is very good but both the M-80 and NITRO sound better. The NITRO has far better dynamics and extension.
The last place to try some things are with the power cables. Quite a few folks have replaced their higher priced PC with the NITRO PC.
The speaker cable will make a difference but I have never heard the Mapleshade cable so I cannot really comment on how much of a difference.