If your computers are working fine as is then I'm not sure you need to tweak anything, they seem fine for what you're using them for.
But, if you want to max your capabilities with what you have...
Your sig says you have 2x GTX 460s, one in each rig, I'd take the one out of one build and SLi it in the other.
The Intel build is x16/x4 (as long as you aren't using a PCIe x1 slot) so it may bottleneck a little.
But, while the AMD build should run x16/x8 or x8/x8, you may need a hack to run SLi on it.
Whichever build you take the 460 out of I'd put the 6870 in.
Then put the 850w PSU in whichever build has the SLi, and 650w in the build with the 6870.
If you're worried about efficiency swap the XFX 850w for the OCZ 850w Gold, whichever build is running SLi.
But, like I said, if its working well as is, probably not worth the effort to swap everything around.
Your best bet is to probably sell all those unopened components, then use the $ to take the wife out to a fancy dinner