Well, I know nothing much about either Thunderbolt OR using an Apple converter, so hopefully some one that DOES know will post some helpful info for you.
With regard to a couple of other things you mentioned in your original post:
1) CPU - while the Intel i7's have the best speed, there ARE some really good CPU's available from AMD - in fact I have 3 desktops running with AMD CPU's and all are CRAZY fast running Sonar or other music applications. The reason I mention this is that you can get an 8-core AMD CPU and add a nice motherboard to the bundle deal for anywhere from around $110 to about $170, which is WAY less costly than for an Intel i7 and a motherboard for it. (some Intel-ready motherboards cost upwards of $200, not counting the CPU, which could be anywhere from around $225-$375 or more. Some retailers offer AMD bundle deals, where if you buy the motherboard and AMD CPU at the same time, you can get one of several motherboards to pick from for anywhere from NO cost up to about $50-$60 for the motherboard.
2) With regard to Cakewalk licensing - the license agreements for Cakewalk recording software DOES allow you to install the software on a 2nd, or even a 3rd machine, BUT you are NOT allowed to be running Sonar on more than a SINGLE computer at a time. So, whichever computer you want to use, at any given time, is FINE - just please just run a single Sonar on a single computer at any one time. I have 3 computers loaded with Sonar, and am following the license agreements by running it on a single computer - picking which computer depends on what I am doing and where I physically AM.
3) I would suggest you do some additional research on Windows and Thunderbolt - I believe there may well be support for it with Windows 10 - I recently say something about it all, but did not pay any attention, because I was in the middle of hooking up gear. Anyways, you will also want to gauge whether or not your existing audio interface is worth investing in additional hardware to keep it running, versus looking at a more current audio interface. If they have drivers for Windows 10 for your current interface, then that's GREAT news, as they are seemingly going to continue support for it for at least a while. I ALSO want to say that I believe Jim Rosenberry recently posted in I believe the Computers forum, something about CRAZY low latency possible with Thunderbolt interfaces in Windows - like being able to go down for ASIO Buffer Size to as low as 32 or even 16 samples, and getting something less then 3 or 4 milliseconds. Now THAT is a great deal, though I am quite content running my setup at a Sample Rate of 48 k and an ASIO Buffer Size of 128. I CAN go down to 64, but I leave it at 128 because I still have no noticeable lag, and really never have to worry about monitoring/tweaking things.
I hope you have a BLAST with whatever you end up with - There are some national retailers with really really good prices - AND some of them price match. I happen to usually use a place called Micro Center -
www.microcenter.com because I am happy with their prices and customer service. They ship, and have 30+ stores around the US. I believe New Egg, and others may well also price match.
Bob Bone