If your build uses an inline DC "brick" for power, try getting a second one and swapping that. The switching supplies that tend to get used in Eurorack can spit out a lot of high frequency hash, although most of the time it's way on up in the ultrasonic range. However, switching supplies can make audible high frequency noise if/when certain components in them are in the process of failing. Also, recheck your amperage draw now that you've added new modules; you might be too close to the P/S's maximum current load by accident, and this would definitely stress the "brick" as a result.
And yes, you CAN use a brick supply that has a higher output than the one you currently have. If you're closing in on that current maximum on any of the DC rails, I'd suggest that as a worthwhile purchase.