I'm surprised there's no thread(s) on this forum regarding the turnkey internet remote capability of the TS590S.
Basically, the hardware required is the host TS590S radio/station, two computers (1 host, 1 remote), internet or intranet, a USB cable with mini A (like a printer USB cable), basic PC headset, and you're in business. No interface boxes, etc., required.
For software at the host/radio, you'll need the Kenwood ARHP-590 host connect app and a VOIP app (I use Skype). Kenwood makes a VOIP app avail called ARVP-10H (host), but Skype works fine, multiple other non radio uses, etc. Skype allows simultaneous voice and texting.
For software at the remote computer (netbook for me), you'll need the Kenwood ARCP-590 rig control app, as well as Skype or the Kenwood VOIP ARVP-10R (remote). If your remote computer does not have at least 768H, (10.1" Netbooks are typically 600H, 11"+ are 768H or higher), you'll lose the extreme bottom of the ARCP-590 GUI screen, but no biggie.
I did not find the Kenwood sound device control app, ARUA-10, to be needed for basic ops. Just open sound card settings on host PC and set in/out to USB codec. For remote, leave sound set to normal soundcard settings. Note, Skype also has lots of sound settings, ability to set sound devices(s), etc.
For a headset, I use a Logitech, get decent audio reports. Besides SSB, will do CW right from GUI window opened in ARCP-590 program, though slower break in required.
All the Kenwood software is free. Skype, with regard to what we're trying to do here, is free.
You'll need to address opening the 50,000 port in your router/modem to the ARCP-590 and ARHP-590 apps, and also dealing with a dynamic IP address for internet ops (not intranet) if applicable. ATT Uverse appears to be static, at least so far. As mentioned in other threads, there are services that will chase your dynamic IP, substitute for entering an actual IP address.
Other considerations are remote antenna/power connect/disconnect schemes.
Many thanks to KA1GJU/Kriss and N1FCC/Dave, for all their help. Two really smart guys.