Thom,
I don't work with Windoze much any more, so most of your questions no longer apply to my new situation.
If it was me, I'd stick with the hardware synths and your current PC.
Then, download a Linux music distribution, and learn how to run it on your computer as a second operating system - time consuming, but worth it. And very little load on your processor, RAM, and harddrive. Once you have the Linux O/S under your belt, get an M-Audio soundcard and the M-Audio controller. M-Audio works well with Linux.
With the JACK audio connection kit in Linux, ASIO is not necessary, and there are
dozens of free, highly functional softsynths and sequencers available from the open-source community. And you'll be free of corporate shenanigans - forever. No viruses, no meltdowns, loads of new software, and frequent free upgrades to your existing arsenal.
It works for me...