Don't let the outdated year of Synergy fool you if you check it out - it works well and has not been updated because it works. That is if you get it set up properly. It's quite easier for the pc side but can confuse people when configuring it for Mac.
If using one computer or the other is all you need to do (as it sounds like it is) your KVM should do the trick. They work fine for Macs as they do for PC's or amongst mixed boxes.
On the software side remote desktop is always good. Or a good free remote access software that plays well now with Macs & PCs is LogMeIn. It has a very nice interface and the free version is all many people need (at the time of this post the free version does not expire). For what it's worth when I was a system admin for a few years the company I worked for used LogMeIn (Pro Version) as our main remote access tool. I still use the free version to work on my office computer from home/everywhere.
As for windows keyboards and mice most work on newer Macs. There are a few that have features not fully supported, but for the most part windows keyboards and mice plug in and work seamlessly. I use the Logitech G15 Keyboard (full features all working including LCD Display) and the MX518 mouse (all buttons supported and working) on my iMac. Although I admit to already putting the Apple keyboard and mouse back when tidying up for company to come over!
I also carry a Microsoft mini wireless laptop mouse in my MBP sleeve that works fine if and when I use it.
* Edit to say have fun buying your new mac! You'll like it no matter which one you get. *