Virtual KVM for Windows/Linux

I was wondering if anyone had any experience/recommendations for using multiple computers and operating systems via one keyboard/mouse...

I'm currently using Symless Synergy, which is cross-platform (Windows/Linux/Mac), uses SSL encryption, and requires practically no setup, but has a few limitations:

• No drag & drop/ copy & paste support for files (you can only copy & paste text)
  
• No monitor switching (so, I guess it's technically a KM rather than KVM..)
  
• No audio sharing (not really an issue since I've got a Pioneer DJM-850, but it'd be nice for the sake of having fewer cables)
  

Now, Stardock Multiplicity looks like it does all of these things, but unfortunately it's Windows-only and I want to be able to access an Ubuntu box in addition to a couple of Windows machines.

Is there a logical/practical way to use multiple tools? Perhaps Multiplicity for Windows->Windows interactions and Synergy for Windows->Linux interactions, or maybe a combination of software and a hardware KVM switch, or maybe a remote desktop tool somewhere in the mix.. ?

Just don't wanna reinvent the wheel or overly complicate things if it's not necessary